A386531 E.g.f. A(x) satisfies A(x) = exp(x + x^3/6 * A''(x)).
1, 1, 1, 2, 13, 181, 4551, 188021, 11924753, 1103029649, 142906232381, 25095114042461, 5813156139567261, 1736262706526700925, 655797361805578202939, 308047913827328021014851, 177358895717746915172030241, 123578165227603044619210348321
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]=v[i]+sum(j=0, i-1, (1+j)*sum(k=1, 2, stirling(2, k, 1)*j^k)*binomial(i-1, j)*v[j+1]*v[i-j])/6); v;
Formula
a(0) = 1; a(n) = a(n-1) + (1/6) * Sum_{k=0..n-1} (-k + k^3) * binomial(n-1,k) * a(k) * a(n-1-k).