|
|
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
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
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
|
|
|
EXTENSIONS
|
More terms from J. Mulder (jasper.mulder(AT)planet.nl), Jan 25 2010
|
|
STATUS
|
approved
|
|
|
|