VOOZH about

URL: https://oeis.org/A275769

⇱ A275769 - OEIS

login
A275769
Least k such that n divides sigma(k!) (k > 0).
1
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
1,2
EXAMPLE
a(5) = 4 because sigma(4!) = 60 is divisible by 5.
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 *)
PROG
(PARI) a(n) = {my(k=1); while(sigma(k!) % n != 0, k++); k; }
CROSSREFS
Sequence in context: A221529 A105161 A383972 * A094365 A272886 A098822
KEYWORD
nonn
AUTHOR
Altug Alkan, Aug 08 2016
STATUS
approved