A275769 Least k such that n divides sigma(k!) (k > 0).

1, 3, 2, 3, 4, 3, 10, 5, 5, 4, 9, 3, 6, 10, 4, 7, 8, 5, 14, 4, 11, 9, 12, 5, 21, 6, 14, 10, 42, 4, 6, 11, 9, 8, 14, 5, 36, 14, 6, 5, 22, 11, 35, 9, 5, 12, 24, 7, 13, 21, 8, 7, 69, 14, 9, 10, 14, 42, 60, 4, 21, 6, 14, 12, 8, 9, 45, 8, 12, 14, 20, 5, 10, 36, 21, 14, 10, 6, 40, 8, 14, 22, 81, 11

Offset: 1

Author

Altug Alkan, Aug 08 2016

Keywords

• nonn

Examples

			a(5) = 4 because sigma(4!) = 60 is divisible by 5.
		

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000203, A062569.

Programs

Mathematica

Table[k = 1; While[! Divisible[DivisorSigma[1, k!], n], k++]; k, {n, 84}] (* Michael De Vlieger, Aug 08 2016 *)
Module[{nn=100,sk},sk=Table[{k,DivisorSigma[1,k!]},{k,nn}];Table[SelectFirst[sk,Mod[#[[2]],n]==0&],{n,nn}]][[;;,1]] (* Harvey P. Dale, Nov 28 2024 *)

PARI

a(n) = {my(k=1); while(sigma(k!) % n != 0, k++); k; }