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A113037 Number of solutions to +- 1 +- 2 +- .. +- n = 3. 2
0, 0, 1, 0, 0, 3, 5, 0, 0, 23, 39, 0, 0, 219, 396, 0, 0, 2406, 4435, 0, 0, 28431, 53167, 0, 0, 353500, 667874, 0, 0, 4557831, 8675836, 0, 0, 60382450, 115601178, 0, 0, 816998489, 1571272955, 0, 0, 11242173783, 21701318843, 0, 0, 156841667096 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,6

LINKS

Ray Chandler, Table of n, a(n) for n = 0..3340 (terms < 10^1000)

FORMULA

a(n) is the coefficient of x^3 in product(x^(-k)+x^k, k=1..n).

MAPLE

A113037:= proc(n) local i, j, p, t; t:= NULL; for j to n do p:=1; for i to j do p:=p*(x^(-i)+x^i); od; t:=t, coeff(p, x, 3); od; t; end;

MATHEMATICA

nmax = 50; d = {1}; a1 = {};

Do[

  i = Ceiling[Length[d]/2] + 3;

  AppendTo[a1, If[i > Length[d], 0, d[[i]]]];

  d = PadLeft[d, Length[d] + 2 n] + PadRight[d, Length[d] + 2 n];

  , {n, nmax}];

a1 (* Ray Chandler, Mar 14 2014 *)

CROSSREFS

Cf. A058377, A063865, A063866.

Sequence in context: A059107 A025115 A230424 * A063866 A059106 A318521

Adjacent sequences:  A113034 A113035 A113036 * A113038 A113039 A113040

KEYWORD

nonn

AUTHOR

Floor van Lamoen, Oct 11 2005

STATUS

approved

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Last modified October 17 19:44 EDT 2019. Contains 328128 sequences. (Running on oeis4.)