A340731 Numbers k such that A067439(k) is prime.

10, 15, 25, 27, 29, 31, 33, 36, 37, 44, 54, 64, 69, 78, 81, 82, 88, 102, 106, 110, 121, 142, 148, 177, 183, 192, 211, 212, 240, 270, 272, 274, 280, 314, 332, 337, 338, 344, 367, 381, 384, 404, 412, 421, 429, 434, 460, 463, 467, 490, 502, 511, 519, 523, 530, 551, 559, 584, 586, 588, 614, 624, 628

Offset: 1

Author

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

Keywords

• nonn

Examples

			a(3) = 25 is a term because A067439(25) = 83 is prime.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A067439, A340736.

Programs

Maple

filter:= proc(n) local t,k;
   isprime(add(`if`(igcd(n,k)=1, n mod k, 0),k=2..n-1))
end proc:
select(filter, [$1..1000]);

PARI

isok(n) = isprime(sum(i=1, n-1, if(gcd(n, i)==1, n%i))); \\ Michel Marcus, Jan 18 2021