A367924 Expansion of e.g.f. 1/(3 - x - 2*exp(x)).
1, 3, 20, 200, 2666, 44422, 888214, 20719722, 552385386, 16567346630, 552104425070, 20238679934002, 809341290336274, 35062535546332062, 1635835480858764342, 81770970437144725034, 4360009179878123161658, 247004345719314584973430
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]=i*v[i]+2*sum(j=1, i, binomial(i, j)*v[i-j+1])); v;
Formula
a(0) = 1; a(n) = n * a(n-1) + 2 * Sum_{k=1..n} binomial(n,k) * a(n-k).