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A321435 Expansion of Product_{1 <= i <= j} (1 + x^(i^2 + j^2)).

%I A321435 #14 Apr 21 2024 11:39:43
%S A321435 1,0,1,0,0,1,0,1,1,0,2,0,1,2,0,3,0,2,3,1,4,1,2,4,1,6,3,4,6,2,7,5,6,8,
%T A321435 5,9,7,9,10,9,12,10,13,14,13,18,13,19,17,18,25,19,28,24,25,33,26,36,
%U A321435 35,33,46,35,47,48,44,61,48,62,65,60,78,68,79,87,79,101,93
%N A321435 Expansion of Product_{1 <= i <= j} (1 + x^(i^2 + j^2)).
%H A321435 Robert Israel, <a href="/A321435/b321435.txt">Table of n, a(n) for n = 0..10000</a>
%F A321435 G.f.: Product_{k>0} (1 + x^k)^A025426(k).
%p A321435 N:= 100: # for a(0)..a(N)
%p A321435 P:= 1:
%p A321435 for i from 1 to floor(sqrt(N)) do
%p A321435   for j from i while i^2 + j^2 <= N do
%p A321435     P:= P * (1 + x^(i^2 + j^2))
%p A321435 od od:
%p A321435 S:= series(P,x,N+1):
%p A321435 seq(coeff(S,x,k),k=0..N); # _Robert Israel_, Apr 21 2024
%Y A321435 Cf. A025426, A321423, A321428, A321436, A321437.
%K A321435 nonn
%O A321435 0,11
%A A321435 _Seiichi Manyama_, Nov 09 2018