A112289 Denominator of sum{k=1 to n} 1/s(n,k), where s(n,k) is an unsigned Stirling number of the first kind.

1, 1, 6, 33, 4200, 4192200, 1705200, 77892963984, 10086416728304192640, 126556188275836361347200, 451535899566923284351392000, 1253032399528279799996000622278320876800

Offset

1,3

Links

Table of n, a(n) for n=1..12.

Example

a(4) = 33, the denominator of 1/6 + 1/11 + 1/6 + 1 = 47/33.
The first few fractions are: 1, 2, 11/6, 47/33, 4999/4200.

Maple

with(combinat): a:=n->denom(sum(1/abs(stirling1(n, k)), k=1..n)): seq(a(n), n=1..14); # Emeric Deutsch, Sep 02 2005

Mathematica

f[n_] := Sum[1/Abs[StirlingS1[n, k]], {k, n}]; Table[Denominator[f[n]], {n, 15}] (* Ray Chandler, Sep 02 2005 *)

Prog

(PARI) a(n) = denominator(sum(k=1, n, 1/abs(stirling(n, k, 1)))); \\ Michel Marcus, Aug 17 2019

Crossrefs

Cf. A112288.

Sequence in context: A046707 A337825 A183466 * A354479 A283232 A190644

Adjacent sequences: A112286 A112287 A112288 * A112290 A112291 A112292

Keyword

nonn,frac

Author

Leroy Quet, Sep 01 2005

Extensions

Extended by Emeric Deutsch and Ray Chandler, Sep 02 2005

Status

approved