A112288 Numerator of sum{k=1 to n} 1/s(n,k), where s(n,k) is an unsigned Stirling number of the first kind.

1, 2, 11, 47, 4999, 4589867, 1802849, 80995354865, 10388318700333839827, 129530631982136545940863, 460116344514106299899953231, 1272711183040784735474188752842879054737

Offset: 1

Author

Leroy Quet, Sep 01 2005

Keywords

• nonn
• frac

Comments

4 consecutive values are primes: 2, 11, 47, 4999. - Jonathan Vos Post, Sep 08 2005

Examples

			a(4) = 47, the numerator 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. A112289.

Programs

Maple

a := n -> numer(add(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[Numerator[f[n]], {n, 15}] (* Ray Chandler, Sep 02 2005 *)

PARI

a(n) = numerator(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