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%I #13 May 13 2013 01:20:37
%S 2,4,8,16,24,40,68,103,162,236,344,453,612,790,994,1229,1432,1782,
%T 2134,2517,2968,3460,3974,4543,5160,5822,6546,7347,8184,9080,10058,
%U 11075,12166,13316,14536,15837,17202,18654,20156,21765,23450,25212,27074,29001,31032,33158,35370,37679,40070,42578
%N a(n) is the number of terms in the expansion of (x-y)*(x^4-y^4)*(x^9-y^9)*...*(x^(n^2)-y^(n^2)).
%C In the definition one can take y=1. Thus the sequence becomes the number of terms in the polynomial of the product{k=1..n} (1-x^(k^2)).
%t a[n_] := Length@ ExpandAll@ Product[(1 - x^(k^2)), {k, n}]; Array[f, 40]
%o (PARI) a(n)=my(P=prod(k=1,n,1-'x^k^2)); sum(i=0, poldegree(P), polcoeff(P,i)!=0) \\ _Charles R Greathouse IV_, May 10 2013
%Y Cf. A000124, A086781, A086795, A086796, A086817.
%K nonn
%O 1,1
%A Yuval Dekel (dekelyuval(AT)hotmail.com) and _Robert G. Wilson v_, May 10 2013
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