|
| |
|
|
A121860
|
|
Sum_{d|n} n!/(d!*(n/d)!).
|
|
0
| |
|
|
1, 2, 2, 8, 2, 122, 2, 1682, 10082, 30242, 2, 7318082, 2, 17297282, 3632428802, 36843206402, 2, 2981705126402, 2, 1690185726028802, 3379030566912002, 28158588057602, 2, 76941821303636889602, 1077167364120207360002
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,2
|
|
|
COMMENTS
| a(n) = 2 for prime n. It appears that all a(n) belong to A100195[n] Numbers n such that the denominator of BernoulliB[n] is a record. - Alexander Adamchuk (alex(AT)kolmogorov.com), Sep 09 2006
a(n) = 2 iff n is prime.
|
|
|
FORMULA
| E.g.f.: Sum_{k>0} (exp(x^k)-1)/k!.
|
|
|
MATHEMATICA
| f[n_] := Block[{d = Divisors@n}, Plus @@ (n!/(d! (n/d)!))]; Array[f, 25] - Robert G. Wilson v Sep 11 2006
|
|
|
CROSSREFS
| Cf. A057625, A100195.
Sequence in context: A086328 A095997 A056189 * A021442 A166853 A143440
Adjacent sequences: A121857 A121858 A121859 * A121861 A121862 A121863
|
|
|
KEYWORD
| easy,nonn
|
|
|
AUTHOR
| Vladeta Jovovic (vladeta(AT)eunet.rs), Sep 09 2006
|
|
|
EXTENSIONS
| More terms from Robert G. Wilson v Sep 11 2006
|
| |
|
|
