How to find a difference polynomial?

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SUMMARY

The discussion focuses on deriving a polynomial function, f(n), for the sequence {a_n} defined by a_0 = 3 and a_n+1 = a_n + (n+1)^2. The sequence's differences reveal a pattern, leading to the conclusion that the differences 1, 4, 9 correspond to n^2. This indicates that the polynomial f(n) is cubic, as the degree of the polynomial is one higher than the degree of the difference sequence. The user is encouraged to prove this characteristic and find the specific cubic polynomial.

PREREQUISITES
  • Understanding of polynomial functions and their degrees
  • Familiarity with difference sequences and finite differences
  • Knowledge of combinatorial coefficients, specifically C(n, r)
  • Basic calculus concepts related to summation and limits
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  • Research how to derive polynomial functions from difference sequences
  • Study the properties of finite differences and their applications in polynomial interpolation
  • Learn about combinatorial coefficients and their role in polynomial expansions
  • Explore proofs related to the relationship between the degree of a polynomial and its difference sequences
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Students in mathematics, particularly those studying sequences and series, educators teaching polynomial functions, and anyone interested in combinatorial mathematics and its applications.

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Homework Statement



Let {a_n} be the sequence 3, 4, 8, 17,..., where a_0 = 3 and a_n+1 = a_n + (n+1)^2, n greater than or equal to 0. Find a polynomial such that a_n = f(n)

Homework Equations



f(n) = summation from r=0 to infinity of C(n,r) delta^r a_0

The Attempt at a Solution



I just have no idea how to start it. I have: f(n) = 3C(n, 0) + 4C(n, 1) + 8C(n,2) + something?
 
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Look at the differences
4-3=1
8-4=4
17-8=9

1,4,9,... is just the sequence for n2

So f(n+1)-f(n) = n2. If the difference has degree k, the actual polynomial has degree k+1 (something you should try proving) so find a cubic polynomial with this characteristic
 

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