A347801 Expansion of ( Sum_{k>=0} k^2 * q^(k^2) )^2.
0, 0, 1, 0, 0, 8, 0, 0, 16, 0, 18, 0, 0, 72, 0, 0, 0, 32, 81, 0, 128, 0, 0, 0, 0, 288, 50, 0, 0, 200, 0, 0, 256, 0, 450, 0, 0, 72, 0, 0, 288, 800, 0, 0, 0, 648, 0, 0, 0, 0, 723, 0, 1152, 392, 0, 0, 0, 0, 882, 0, 0, 1800, 0, 0, 0, 1696, 0, 0, 512, 0, 0, 0, 1296, 1152, 2450, 0, 0, 0, 0, 0, 2048, 0, 162, 0, 0, 4176, 0, 0, 0, 3200, 1458
Offset: 0
Keywords
Links
- Seiichi Manyama, Table of n, a(n) for n = 0..10000
Programs
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PARI
a(n) = sum(i=1, n, sum(j=1, n, (i^2+j^2==n)*(i*j)^2));
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PARI
my(N=99, x='x+O('x^N)); concat([0, 0], Vec(sum(k=0, sqrtint(N), k^2*x^k^2)^2))
Formula
a(n) is sum of i^2 * j^2 for positive integers i,j such that i^2+j^2=n.