A320061 Numbers k such that A215240(k) is prime.

1, 2, 144, 264, 540, 720, 888, 928, 1012, 1368, 1452, 1476, 1656, 1764, 1800, 1836, 1960, 2024, 2392, 2664, 2712, 2968, 3444, 3680, 3720, 3808, 4248, 4284, 4352, 4368, 4776, 5060, 5412, 5600, 6516, 6624, 6840, 6984, 7040, 7168, 7176, 7600, 7836, 7860, 8052, 8160, 8196, 8304, 8496, 8848, 9144

Offset: 1

Author

Robert Israel, Oct 04 2018

Keywords

• nonn

Examples

			a(3)=144 is in the sequence because phi(h)=144 for h = 185, 219, 273, 285, 292, 296, 304, 315, 364, 370, 380, 432, 438, 444, 456, 468, 504, 540, 546, 570, 630, and the sum of those is the prime 8311.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000
• Max Alekseyev, PARI scripts for various problems (see invphi.gp there).

Crossrefs

Cf. A215240, A320041.

Programs

Maple

select(n -> isprime(convert(numtheory:-invphi(n),`+`)), [$1..10000]);

PARI

isok(n) = isprime(vecsum(invphi(n))); \\ Michel Marcus, Oct 05 2018