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%I #11 Mar 02 2015 16:08:50
%S 0,0,1,0,0,3,5,0,0,23,39,0,0,219,396,0,0,2406,4435,0,0,28431,53167,0,
%T 0,353500,667874,0,0,4557831,8675836,0,0,60382450,115601178,0,0,
%U 816998489,1571272955,0,0,11242173783,21701318843,0,0,156841667096
%N Number of solutions to +- 1 +- 2 +- .. +- n = 3.
%H Ray Chandler, <a href="/A113037/b113037.txt">Table of n, a(n) for n = 0..3340</a> (terms < 10^1000)
%F a(n) is the coefficient of x^3 in product(x^(-k)+x^k, k=1..n).
%p 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;
%t nmax = 50; d = {1}; a1 = {};
%t Do[
%t i = Ceiling[Length[d]/2] + 3;
%t AppendTo[a1, If[i > Length[d], 0, d[[i]]]];
%t d = PadLeft[d, Length[d] + 2 n] + PadRight[d, Length[d] + 2 n];
%t , {n, nmax}];
%t a1 (* _Ray Chandler_, Mar 14 2014 *)
%Y Cf. A058377, A063865, A063866.
%K nonn
%O 0,6
%A _Floor van Lamoen_, Oct 11 2005
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