A359660 a(n) = Sum_{k=0..n} k^(2 * (n-k) + 1).
0, 1, 3, 12, 64, 441, 3855, 41464, 533736, 8071785, 141351715, 2829417276, 64038928728, 1624347614737, 45822087138879, 1427872211276376, 48858282302548240, 1826209988254883889, 74216973833968292451, 3265676709281560408780
Offset: 0
Programs
-
PARI
a(n, s=1, t=2) = sum(k=0, n, k^(t*(n-k)+s));
-
PARI
my(N=20, x='x+O('x^N)); concat(0, Vec(sum(k=0, N, k*x^k/(1-k^2*x))))
Formula
G.f.: Sum_{k>=0} k * x^k/(1 - k^2 * x).