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

Author

Leroy Quet, Sep 01 2005

Keywords

• nonn
• frac

Examples

			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.
		

Crossrefs

Cf. A112288.

Programs

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 *)

PARI

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

Extensions

Extended by Emeric Deutsch and Ray Chandler, Sep 02 2005