OFFSET
1,4
LINKS
Eric Weisstein's World of Mathematics, Graph Cycle
FORMULA
a(n) = sum(k=1..n,A002807(k)).
a(n) ~ exp(1) * (n-1)! / 2. - Vaclav Kotesovec, Jun 09 2019
MATHEMATICA
Table[Sum[Binomial[k, l] (l - 1)!, {k, n}, {l, 3, k}]/2, {n, 20}]
Table[Sum[k (2 HypergeometricPFQ[{1, 1, 1 - k}, {2}, -1] - k - 1)/4, {k, n}], {n, 20}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Eric W. Weisstein, Jul 14 2017
STATUS
approved