login
A087906
a(n) = Sum_{d|n} (n-1)!/(d-1)!.
16
1, 2, 3, 13, 25, 301, 721, 10921, 60481, 740881, 3628801, 106777441, 479001601, 12462690241, 134399865601, 2833553923201, 20922789888001, 892191453753601, 6402373705728001, 268633265290790401, 3652732042831872001, 102181898422712908801, 1124000727777607680001
OFFSET
1,2
LINKS
FORMULA
E.g.f.: Sum_{k>0} (exp(x^k)-1)/k = -Sum_{k>0} log(1-x^k)/k!.
MATHEMATICA
Array[n \[Function] DivisorSum[n, (n - 1)!/(# - 1)! &], 25] (* J. Mulder (jasper.mulder(AT)planet.nl), Jan 25 2010 *)
PROG
(PARI) a(n)=sumdiv(n, d, (n-1)!/(d-1)!); \\ Joerg Arndt, May 21 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladeta Jovovic, Oct 15 2003
EXTENSIONS
More terms from J. Mulder (jasper.mulder(AT)planet.nl), Jan 25 2010
STATUS
approved