A365989 Expansion of e.g.f. exp( Sum_{k>=0} x^(5*k+4) / (5*k+4) ).
1, 0, 0, 0, 6, 0, 0, 0, 1260, 40320, 0, 0, 1247400, 172972800, 6227020800, 0, 3405402000, 1235025792000, 153848927232000, 6402373705728000, 19799007228000, 14783258730240000, 4243499220280320000, 545332851008225280000, 25852227123135781368000
Offset: 0
Keywords
Programs
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PARI
my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(sum(k=0, N\5, x^(5*k+4)/(5*k+4)))))
Formula
a(0) = 1; a(n) = (n-1)! * Sum_{k=0..floor((n-4)/5)} a(n-5*k-4)/(n-5*k-4)!.