What is Integers: Definition and 472 Discussions

An integer (from the Latin integer meaning "whole") is colloquially defined as a number that can be written without a fractional component. For example, 21, 4, 0, and −2048 are integers, while 9.75, 5+1/2, and √2 are not.
The set of integers consists of zero (0), the positive natural numbers (1, 2, 3, ...), also called whole numbers or counting numbers, and their additive inverses (the negative integers, i.e., −1, −2, −3, ...). The set of integers is often denoted by the boldface (Z) or blackboard bold



(

Z

)


{\displaystyle (\mathbb {Z} )}
letter "Z"—standing originally for the German word Zahlen ("numbers").ℤ is a subset of the set of all rational numbers ℚ, which in turn is a subset of the real numbers ℝ. Like the natural numbers, ℤ is countably infinite.
The integers form the smallest group and the smallest ring containing the natural numbers. In algebraic number theory, the integers are sometimes qualified as rational integers to distinguish them from the more general algebraic integers. In fact, (rational) integers are algebraic integers that are also rational numbers.

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  1. E

    How many ways can you express n as the sum of positive integers?

    [SOLVED] expressions of integers Homework Statement Let n be a positive integer. How many ways can you express a as the sum of positive integers? Order of addition does not matter. EDIT: change "a" to "n" in the second sentence Homework Equations The Attempt at a Solution Let f(x) be the...
  2. G

    Lecture notes regarding integers ?

    Hey guys , was wondering if you guys know of any lecture notes regarding integers ? i would like to further my knowledge in this field ... cheers :smile:
  3. E

    Solving the Larson Problem: Constructing 0 & 1 Divisible Integers

    [SOLVED] larson problem Homework Statement Note: sorry to Loren Larson for constantly misspelling your last name as "larsen" and sorry to everyone who has been wondering who Loren Larsen is. Given an integer n, show that an integer can always be found that contains only the digits 0 and 1 (in...
  4. S

    Counterexample so that (ab)^i=a^ib^i for two consecutive integers

    counterexample so that (ab)^i=a^ib^i for two consecutive integers for any a and b in a group G does not imply that G is abelian. this is a problem in herstein and I'm struggling to find an example. The previous problem to show that if (ab)^i=a^ib^i for 3 consecutive integers then G is...
  5. P

    Find Integer Solutions for Tricky Equations with Maximum Error of +- pi/7

    Given 3 equations: 1) 1/2pi + 2Pi(x) = 3.90625F 2) pi + 2Pi(y) = 7.65625F 3) 3/2pi + 2Pi(z) = 11.2500F Find such F so that x, y and z are integers; maximum error on the left side can be +- pi/7. How would you tackle this one? I am still trial'n'erroring..
  6. E

    Proving Total Order of Integers through LCM and GCD Relationship

    Homework Statement http://math.stanford.edu/~vakil/putnam07/07putnam2.pdf I am working on problem 5. It is clear that the integers will not change if they can be totally ordered by divisibility, but I need help proving that they will reach such a state. Obviously after every step, the...
  7. S

    Direct Proof With Odd Integers

    Homework Statement If m is an odd integer and n divides m, then n is an odd integer. Homework Equations Odd integers can be written in the form m=2k+1. Since n divides m, there exists an integer p such that m=np The Attempt at a Solution We will assume that m is an odd integer and...
  8. P

    Proof: integers divisibility property

    Someone please help me with this qiestion: Prove that for all integers a, b, and c, if a divides b but not c then a does not divide b + c, but the converse is false. Thanks.
  9. C

    Can I Use Big Integers in C# with GMP on Windows?

    I want to use arbitrarily long integers in Csharp, can you tell me how to declare and use this. Please explain the namespace, classes used as I'm very new to this. Thanks.
  10. I

    Functions that vanish at integers

    We know that the function f(x) = sin(2*pi*x) vanishes at all integers, are there other functions like that and what is the appropriate generalization to higher dimensions? Cheers
  11. D

    Summing sets of inverses of integers

    How can I prove this? Suppose X is a set of 16 distinct positive integers, X=\left\{{x_{1}, \cdots , x_{16}}\right\}. Then, for every X, there exists some integer k\in\left\{{1, \cdots , 8}\right\} and disjoint subsets A,B\subset X A=\left\{a_{1},\cdots\ ,a_{k}\right\} and...
  12. F

    Write a Lisp program to calculate the sum of the first N positive integers

    Help! Please I am trying to write a Lisp program to calculate the sum of the first N positive integers where, for example, when N = 6 the sum of the first N = 21 Any Ideas?
  13. F

    Help - Lisp program to calculate the sum of first N positive integers

    Homework Statement Write a Lisp program to calculate the sum of the first N positive integers where, for example, when N = 6 the sum of the first N = 21. Homework Equations If you try this out in tlisp at http://www.ugcs.caltech.edu/~rona/tlisp/ please note that the syntax for N -...
  14. L

    Algebraic integers of a finite extension of Q has an integral basis

    I already know that this is true for galois extensions of Q... how do you extend this result to any finite extension of Q? I was thinking given a finite extension of Q, call it K... find a galois extension that includes the finite extension, call it L... then somehow use the fact that the...
  15. M

    Congruence of all integers n, 4^n and 1 +3n mod(9)?

    I just took a number theory midterm, the professor had a question the that said "Show by induction that for all integers n, 4^{n} is congruent to 1 +3n mod(9). Now am I crazy or did the professor probably mean to say integers greater or equal to 0, or for any natural number n, ...
  16. D

    Fortran Fortran: Passing integers to type dimension

    Why does does the following code not compile? PROGRAM TYPES INTEGER A(3) A(1)=1 A(2)=2 A(3)=3 CALL SUBR(A) print *,'Done' RETURN END C --- Here is a subroutine ----- SUBROUTINE SUBR(A)...
  17. R

    Gaussian Integers and Pythagorean Triplets

    It is well known that 4n(n+1) + 1 is a square if n is an integer but if n is a Gaussian integer i.e., 4n(n+1) + 1 = A + Bi, then the norm (A^2 + B^2) is always a square! The proof is quite easy since A = u^2 - v^2 and B = 2uv.
  18. K

    Swapping 3 integers in C program

    Hi! i have a problem about swapping three integers in C program. Usually i use the call by reference for two integers only. Now for three i can't get t.
  19. A

    Mathematica What is the mathematical symbol for integers?

    The mathematical symbol for real numbers is R, with another vertical line coming down on the left side of the R. What is the mathematical symbol for integers? can anyone draw it?
  20. F

    Kakuro is based on partitions of integers

    Does anyone do these? Sudoku is based on magic squares, Kakuro is based on partitions of integers. I haven't really tried solving any yet but my first impression was that Kakuro is generally tougher than Sudoku (for me anyway). http://en.wikipedia.org/wiki/Kakuro
  21. F

    Proving Constant Sequence of Positive Integers Starting with n

    Let n be a positive integer. Define a sequence by setting a_1 = n and, for each k > 1, letting a_k be the unique integer in the range [tex]0 \le a_k \le k-1[/itex] for which \displaystyle a_1 + a_2 + \cdots + a_k is divisible by k. For instance, when n = 9 the obtained sequence is \displaystyle...
  22. Saladsamurai

    Prove that sum of two even integers is even

    Okay, I know that this is probably super easy. This is not homework, I just grabbed tis book at the library today and am trying to get familiar with the subject (Abstract Algebra). The book is hella old and doesn't have many of the solutions, especially if the author regarded the solution as...
  23. M

    Understanding Subgroups of Integers: Explained Simply

    Hello all. I reluctantly ask this question because it is probably,as the text states easy, but my desire to clear this point up overides my fear of looking a fool. I quote word for word but will use words instead of the belongs to symbol. A subset S of the set Z of integers is a...
  24. F

    Congruence Classes in Quadratic Integers

    Homework Statement I need to find the congruence classes mod (3 + sqrt(-3))/2 in Q[sqrt(-3)]. Homework Equations None known. The Attempt at a Solution I'm not sure how to go about finding these congruence classes. I know that in the regular integers congruences classes mod x are...
  25. F

    Congruence in Quadratic Integers

    Homework Statement For my number theory course, I'm supposed to come up with a definition of congruence in quadratic integers, and define the operations of addition, subtraction, and multiplication. Homework Equations None known. The Attempt at a Solution I honestly have no real...
  26. J

    Graphing Natural Numbers to Integers

    Hi, just can't get my head around how to draw these three graphs. Any help appreciated. Thanks In each case below, draw the graph of a function f that satisfies the given property. Give an example of a function f : N -> Z that is bijective/that is injective but not surjective/that is...
  27. R

    Integers in Bohr's atomic theory

    Are integers such as n=1,2,3 etc in Bohr's atomic theory, exactly whole numbers or just very close to being whole numbers?
  28. A

    Are There Any Pairs (P,Q) With All Composite Integers Modulo Q?

    Hi! I was thinking about primes and have a bit of a question. I apologize if this is too easy or obvious -- I haven't thought much about it. Take two relatively prime numbers, P and Q. P < Q, and P is not prime. How many pairs (P,Q) are there so that ALL positive integers which are...
  29. D

    Sequence of ratios of primes and integers

    I am fairly certain that \frac{n}{p_n} is not monotone for any n, but I can't give a proof of it without assuming something at least as strong as the twin prime conjecture. I was wondering if anyone has some advice to prove this using known methods?
  30. H

    List of increasing integers algorithm

    Specify the steps of an algorithm that locates an element in a list of increasing integers by successively splitting the list into four sublists of equal (or as close to equal as possible) size, and restricting the search to the appropriate piece. (Hint: see binary search algorithm.) can...
  31. B

    Express the number as a ratio of integers.

    hi I am having trouble with this question: Q:Express the number as a ratio of integers. 9.4(78)bar so 9.4787878787878787878 what is confusing me is the 9.4, and where i should start the series at 78/10^(?) please if someone could help me. ty
  32. M

    How many integers from 1 through 99,999 is the sum of their digits = 9?

    Wow, I'm totally lost on where to start for this one. In this chapter we have been working with r-combinations with repeition allowed and using the form of(r + n - 1) (r ) Where n stands for categories, so if you had 4 categories u would use 3 bars to break up the categories. And r...
  33. C

    C/C++ C++ conversion of integers into strings, how

    how to convert an input of integer(more than 1 character) type into output which is in string in c++
  34. M

    Slight deviation of proof, would it be correct for integers? Review for exam

    Hello everyone. He told us he could of course change the parameters which he will of the proofs we have been working on so I'm testing out some cases but I want to make sure I'm doing it right. Here is an example of a proof the boook had...
  35. M

    Prove that for all integers n, n^2-n+3 is odd. stuck on algebra part

    Prove that for all integers n, n^2-n+3 is odd. stuck on algebra part :( The question in the book is the following bolded statement. Prove that for all integers n, n^2-n+3 is odd. I rewrote it as this, is that right? For all integers n, there exists an integer such that n^2-n+3 is odd...
  36. quasar987

    A formula of the product of the first n integers?

    I'm sure it exists, and it'd help me to have it. Thx!
  37. M

    Proof for al integers n, if n is prime then (-1)^n = -1, can i use counter example?

    Hello everyone. I'm wondering if I'm allowed to use a counter example to disprove this. I'm not sure if I'm understanding the statement correctly though. THe directions are: Determine whether the statement is true or false. Justify your answer with a rpoof or a counterexample. Here is...
  38. B

    Understanding the Integers Modulo n Groups in Abstract Algebra

    We are currently using Dummit & Foote's Abstract Algebra book in a gradute course of the same name. Recently, I had an issue concerning the additive and multiplicative integer groups mod n, which I brought to the professor's attention. The issue deals specifically with the way these groups are...
  39. daniel_i_l

    An infinite amount of integers?

    This is probablly a silly question but it has been bothering me for a while. How can there be for example an infinite amountof integers? each integer has an integer that is smaller than it by one and an any number that is one bigger than a finate number is also finate. doesn't this prove that...
  40. G

    C/C++ Counting Integers: Writing a Program

    How I can write a program which reads a sequence of integers and counts how many there are. Print the count. For example, with input 55 25 1004 4 -6 55 0 55, the output should be 8 because there were eight numbers in the input stream. Please help.
  41. F

    Programming with large integers

    Hi all, I'm doing a little programming at the moment using Dev-C++. I'm writing a windows program, and have all of the stuff like menus, dialog boxs etc sorted out, and now need to get onto the programming that makes the program achieve something. In the program I will be dealing with very large...
  42. K

    Stuck on Math Problem: Find the Integers

    The sum of two intergers is twenty. Five times the smaller interger is two more than twice the larger integer. Find the integers. I'm somehow lost on the problem I tried setting the problem up to solve for the smaller varrible. Making it x & the larger 20-x. Anyway, I came up with 5x...
  43. J

    Determinant of a matrix over the integers mod n

    Hi, I'm curious if the following statement is true for all prime numbers n, \det_{\mathbb{Z}_n}M = (\det_{\mathbb{R}}M)\mod n where \det_F M is the determinant of M over the field F. Thanks. James
  44. E

    How can we solve sums of powers of integers using differences and integrals?

    Let,s suppose we want to do this sum: 1+2^{m}+3^{m}+...+n^{m} n finite then we could use the property of the differences: \sum_{n=0}^{n}(y(k)-y(k-1))=y(n)-y(0) so for any function of the form f(x)=x^{m} m integer you need to solve: y(n)-y(n-1)=n^{m} i don,t know how to...
  45. N

    Primes vs. Integers: Are There More?

    I was having this discussion in my math class today, and my teacher said that it was not something that he couldn't explain in a manner that we would understand. So the question is, are there more positive integers than primes, or no?
  46. S

    Towers of integers and divisibilty by 11

    I'm really stuck on the following problem: I'm trying to determine whether or not 5^10^5^10^5 is divisible by 11... i have tried a few different methods and can't figure this out. I know the trick must have something to do with modulo 11, but I am not sure exactly how to get the...
  47. P

    Understanding Faulhaber's Formula for Sum of Powers of n Integers

    hi everybody, I have a question in math to figure out the general term for the sum of the pth powers of n integers. I found a formula called faulhabers formula to do this question, but I do not understand the method behind it. can someone please help me?
  48. benorin

    Set of p-adic integers is homeomorphic to Cantor set; how?

    Could somebody explain with due brevity why/how the set of p-adic integers is homeomorphic to the Cantor set less one point for any prime p? This is a quote from Wikipedia:Cantor Set: "The Cantor set is also homeomorphic to the p-adic integers, and, if one point is removed from it, to the...
  49. S

    Recursive formula for zeta function of positive even integers

    I was working with Fourier series and I found the following recursive formula for the zeta function: \frac{p \\ \pi^{2p}}{2p+1} + \sum_{k=1}^{p} \frac{(2p)! (-1)^k \pi^{2(p-k)}}{(2(p-k)+1)!} \zeta(2k) = 0 where [itex]\zeta(k)[/tex] is the Riemann zeta function and p is a positive integer. I...
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