A381779 G.f. A(x) satisfies A(x) = (1 + x*A(x)) * C(x*A(x)^3), where C(x) is the g.f. of A000108.
1, 2, 11, 95, 977, 11028, 132029, 1646428, 21155077, 278127359, 3723466202, 50586670945, 695676081162, 9665426437561, 135464096419620, 1912922793362142, 27190770354633287, 388734441118885467, 5586079818959767743, 80638973170989453862, 1168864771263296930809
Offset: 0
Keywords
Programs
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PARI
a(n) = sum(k=0, n, binomial(n+4*k+1, k)*binomial(n+2*k+1, n-k)/(n+4*k+1));
Formula
a(n) = Sum_{k=0..n} binomial(n+4*k+1,k) * binomial(n+2*k+1,n-k)/(n+4*k+1).