A365977 Expansion of e.g.f. 1 / ( 1 - Sum_{k>=0} x^(5*k+1) / (5*k+1) ).
1, 1, 2, 6, 24, 120, 840, 6720, 60480, 604800, 6652800, 83462400, 1138233600, 16746912000, 264176640000, 4444771968000, 80719172352000, 1556132497920000, 31722198842880000, 681437830993920000, 15378172899747840000, 366025806545817600000
Offset: 0
Keywords
Programs
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PARI
my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1-sum(k=0, N\5, x^(5*k+1)/(5*k+1)))))
Formula
a(0) = 1; a(n) = Sum_{k=0..floor((n-1)/5)} (5*k)! * binomial(n,5*k+1) * a(n-5*k-1).