A369693 G.f. satisfies A(x) = 1/(1-x)^4 + x^4*A(x)^4.
1, 4, 10, 20, 36, 72, 220, 936, 4045, 15836, 56174, 187148, 616651, 2114448, 7717752, 29498000, 114243269, 437915876, 1650264874, 6149423732, 22909545269, 86129798600, 327872238092, 1260466647944, 4867739842821, 18801022899756, 72501445905366
Offset: 0
Keywords
Programs
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PARI
a(n) = sum(k=0, n\4, binomial(n+8*k+3, n-4*k)*binomial(4*k, k)/(3*k+1));
Formula
a(n) = Sum_{k=0..floor(n/4)} binomial(n+8*k+3,n-4*k) * binomial(4*k,k) / (3*k+1).