A353301 Numbers k such that A004394(k)+1 is prime.

1, 2, 3, 4, 5, 7, 9, 11, 12, 18, 21, 24, 25, 28, 35, 45, 46, 50, 56, 70, 73, 76, 78, 79, 82, 89, 94, 105, 113, 116, 118, 121, 123, 124, 138, 139, 153, 157, 159, 164, 197, 201, 203, 210, 217, 253, 261, 273, 280, 283, 287, 342, 352, 356, 381, 396, 437, 450, 471

Offset: 1

Author

Amiram Eldar, Apr 10 2022

Keywords

• nonn

Comments

First differs from A306587 at n=11.

Examples

			1 is a term since A004394(1)+1 = 1+1 = 2 is prime.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..300

Crossrefs

Cf. A004394, A072828, A306587, A353300, A353302.

Programs

Mathematica

s = {}; abm = 0; k = 0; Do[ab = DivisorSigma[-1, n]; If[ab > abm, abm = ab; k++; If[PrimeQ[n + 1], AppendTo[s, k]]], {n, 1, 10^6}]; s