A376487 G.f. satisfies A(x) = 1 / (1 - x^4*A(x)^4 * (1 + x)).
1, 0, 0, 0, 1, 1, 0, 0, 5, 10, 5, 0, 35, 105, 105, 35, 285, 1140, 1710, 1140, 2815, 12650, 25300, 25300, 36401, 145036, 356265, 475020, 588145, 1765666, 4893231, 8115800, 10446245, 23513040, 66875620, 130736800, 187081505, 346058115, 927465240
Offset: 0
Keywords
Programs
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PARI
a(n) = sum(k=0, n\4, binomial(5*k, k)*binomial(k, n-4*k)/(4*k+1));
Formula
G.f.: (1/x) * Series_Reversion( x*(1-x^4)/(1+x^5) ).
a(n) = Sum_{k=0..floor(n/4)} binomial(5*k,k) * binomial(k,n-4*k) / (4*k+1).