-1

f(0) = 1
f(1) = 4 f(2) = 13 f(3) = 40 f(4) = 121

what is the function?

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Rather than this site, I suggest the Online Encyclopedia of integer sequences for such questions. oeis.org/search?q=1+4+13+40+121 – Benjamin Young Jan 6 2012 at 15:29
This data does not determine a function: there are infinitely many functions with these values at these points. Indeed, given any such, just add a term with a factor of x(x-1)(x-2)(x-3)(x-4) and you have another. – Alex Collins Jan 6 2012 at 15:54
or just go on as you like after f(4) – Pietro Majer Jan 7 2012 at 11:17

closed as not a real question by Mark Sapir, Henry Cohn, Bill Johnson, Andres Caicedo, Bruce Westbury Jan 6 2012 at 15:59

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