A342630 Numbers k such that A340180(k) is prime.

5, 6, 7, 14, 18, 24, 29, 34, 39, 41, 47, 53, 77, 114, 119, 148, 150, 159, 176, 188, 189, 190, 191, 205, 215, 217, 218, 241, 268, 288, 312, 314, 331, 334, 339, 342, 346, 352, 364, 367, 387, 390, 402, 418, 429, 438, 439, 440, 446, 449, 480, 493, 494, 500, 504, 510, 521, 523, 546, 549, 553, 561, 580

Offset: 1

Author

J. M. Bergot and Robert Israel, Mar 17 2021

Keywords

• nonn

Examples

			a(4) = 14 is a term because A340180(14) = 23 is prime.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..5000

Crossrefs

Cf. A340180.

Programs

Maple

f:= proc(n) local s,k;
  s:= numtheory:-sigma(n);
  add(`if`(igcd(n,k)=1, s mod k, 0),k=1..n-1);
end proc:
select(t -> isprime(f(t)), [$1..1000]);