A349023 G.f. satisfies: A(x) = 1/(1 - x/(1 - x*A(x))^4)^2.
1, 2, 11, 64, 417, 2892, 20941, 156500, 1198049, 9346690, 74042938, 594001236, 4815995027, 39399831458, 324840184326, 2696343599336, 22514057175337, 188977375146888, 1593661234493561, 13495942411592260, 114723671513478118, 978570384358686064
Offset: 0
Keywords
Programs
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PARI
a(n, s=4, t=2) = sum(k=0, n, binomial(t*n-(t-1)*(k-1), k)*binomial(n+(s-1)*k-1, n-k)/(n-k+1));
Formula
If g.f. satisfies: A(x) = 1/(1 - x/(1 - x*A(x))^s)^t, then a(n) = Sum_{k=0..n} binomial(t*n-(t-1)*(k-1),k) * binomial(n+(s-1)*k-1,n-k)/(n-k+1).