OFFSET
0,3
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..200
MATHEMATICA
S[m_, n_] := Binomial[Binomial[m, 2] + n - 1, n];
R[nn_] := Module[{cc = Array[0&, {nn, nn}]}, cc[[1, 1]] = 1; For[m = 1, m <= nn, m++, For[n = 1, n <= nn - 1, n++, cc[[m, n + 1]] = S[m, n] - S[m - 1, n] - Sum[Sum[Binomial[m - 1, i - 1]*cc[[i, j + 1]]*S[m - i, n - j], {j, 1, n}], {i, 2, m - 1}]]]; cc // Transpose];
PROG
(PARI)
Connected(v)={my(u=vector(#v)); for(n=1, #u, u[n]=v[n] - sum(k=1, n-1, binomial(n-1, k)*v[k]*u[n-k])); u}
seq(n)={Vec(vecsum(Connected(vector(2*n, j, 1/(1 - x + O(x*x^n))^binomial(j, 2)))))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Apr 14 2021
STATUS
approved