A368454 Expansion of e.g.f. 2*exp(-x) / (3 - exp(2*x)).
1, 0, 3, 12, 93, 840, 9183, 117012, 1704153, 27921360, 508302363, 10178888412, 222365364213, 5262547606680, 134124963385143, 3662574088282212, 106682195378484273, 3301614846549616800, 108189336403552025523, 3742170760095124874412
Offset: 0
Keywords
Programs
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PARI
a_vector(n) = my(v=vector(n+1)); for(i=0, n, v[i+1]=(-1)^i+sum(j=1, i, 2^(j-1)*binomial(i, j)*v[i-j+1])); v;
Formula
a(n) = (-1)^n + Sum_{k=1..n} 2^(k-1) * binomial(n,k) * a(n-k).