A354696 G.f. A(x) satisfies: A(x) = 1 + x * A(x^4/(1 - x)^4) / (1 - x)^4.
1, 1, 4, 10, 20, 36, 64, 120, 240, 499, 1060, 2314, 5252, 12360, 29632, 70992, 168096, 392465, 905940, 2075314, 4730052, 10735516, 24258688, 54553000, 122076240, 271914499, 603183508, 1333268098, 2937818900, 6455143760, 14146816640, 30929336736, 67473335104
Offset: 0
Keywords
Programs
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PARI
a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=sum(j=0, (i-1)\4, binomial(i+2, 4*j+3)*v[j+1])); v;
Formula
a(0) = 1; a(n) = Sum_{k=0..floor((n-1)/4)} binomial(n+2,4*k+3) * a(k).