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
Keywords
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).
Programs
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Maple
select(n -> isprime(convert(numtheory:-invphi(n),`+`)), [$1..10000]);
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PARI
isok(n) = isprime(vecsum(invphi(n))); \\ Michel Marcus, Oct 05 2018