# Finding the general expression of the nth term

1. Jul 6, 2012

### superconduct

1. The problem statement, all variables and given/known data
Given successive terms of numbers starting from the 1st term:
11, 21, 35, 53, 75, 101,...
What is the general expression of the nth term? where n is positive integer

2. Relevant equations
/

3. The attempt at a solution
Can't find a good attempt.

2. Jul 6, 2012

### micromass

Staff Emeritus
Could this be an arithmetic or geometric sequence??

3. Jul 6, 2012

### Curious3141

Form a new sequence from the differences between successive terms.

4. Jul 6, 2012

### superconduct

sorry I don't know...

how will you determine a general expression for it in this problem without trial and error?

is it like finding a needle in the ocean?

5. Jul 6, 2012

### Staff: Mentor

look at the terms, then form a sequences of differences and what do you get?

10 , 14, 18, 22, 26 ...

look at the differences as a sequence and what do you see?

write an expression to generate the differences sequence

term(n)= term(0) + 4*(n-1) where n=1, 2, 3, 4...

then write an expression to generate your sequence using the differences expression

TERM(n) = TERM(0) + ...

6. Jul 6, 2012

### wiraimperia

Ouw... I think you can use the Sn to calculate the Un...