A067792 a(n) is the least prime >= sigma(n).

2, 3, 5, 7, 7, 13, 11, 17, 13, 19, 13, 29, 17, 29, 29, 31, 19, 41, 23, 43, 37, 37, 29, 61, 31, 43, 41, 59, 31, 73, 37, 67, 53, 59, 53, 97, 41, 61, 59, 97, 43, 97, 47, 89, 79, 73, 53, 127, 59, 97, 73, 101, 59, 127, 73, 127, 83, 97, 61, 173, 67, 97, 107, 127, 89, 149, 71, 127

Offset: 1

Author

Benoit Cloitre, Feb 07 2002

Keywords

• nonn
• look

Links

• Antti Karttunen, Table of n, a(n) for n = 1..16384
• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000203, A007918, A070801, A074495.

Programs

Mathematica

Array[If[PrimeQ@ #, #, NextPrime@ #] &@ DivisorSigma[1, #] &, 68] (* Michael De Vlieger, Nov 16 2017 *)

PARI

A067792(n) = nextprime(sigma(n)); \\ Antti Karttunen, Nov 16 2017

Formula

From Antti Karttunen, Nov 17 2017: (Start)

a(n) = A007918(A000203(n)).

a(n) <= A074495(n).

(End)

Extensions

Definition clarified by Antti Karttunen, Nov 16 2017