A357926 a(n) = Sum_{k=0..floor(n/4)} Stirling2(n - 3*k,n - 4*k).
1, 1, 1, 1, 1, 2, 4, 7, 11, 17, 29, 54, 102, 187, 337, 619, 1179, 2298, 4488, 8733, 17085, 33931, 68407, 139030, 283474, 580477, 1198195, 2496661, 5241757, 11061986, 23453024, 50008919, 107338755, 231825945, 503294589, 1097731342, 2405837254, 5300147291
Offset: 0
Keywords
Programs
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PARI
a(n) = sum(k=0, n\4, stirling(n-3*k, n-4*k, 2));
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PARI
my(N=40, x='x+O('x^N)); Vec(sum(k=0, N, x^k/prod(j=1, k, 1-j*x^4)))
Formula
G.f.: Sum_{k>=0} x^k/Product_{j=1..k} (1 - j * x^4).