|
%I #11 Oct 05 2018 05:06:10
%S 1,2,144,264,540,720,888,928,1012,1368,1452,1476,1656,1764,1800,1836,
%T 1960,2024,2392,2664,2712,2968,3444,3680,3720,3808,4248,4284,4352,
%U 4368,4776,5060,5412,5600,6516,6624,6840,6984,7040,7168,7176,7600,7836,7860,8052,8160,8196,8304,8496,8848,9144
%N Numbers k such that A215240(k) is prime.
%H Robert Israel, <a href="/A320061/b320061.txt">Table of n, a(n) for n = 1..10000</a>
%H Max Alekseyev, <a href="http://home.gwu.edu/~maxal/gpscripts/">PARI scripts for various problems</a> (see invphi.gp there).
%e 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.
%p select(n -> isprime(convert(numtheory:-invphi(n),`+`)), [$1..10000]);
%o (PARI) isok(n) = isprime(vecsum(invphi(n))); \\ _Michel Marcus_, Oct 05 2018
%Y Cf. A215240, A320041.
%K nonn
%O 1,2
%A _Robert Israel_, Oct 04 2018
|
