A258977 - OEIS

%I #24 Sep 08 2022 08:46:13

%S 2,17,37,197,577,577,401,1297,577,1601,3137,2917,3137,8101,7057,15377,

%T 2917,14401,14401,8101,7057,15877,5477,15377,15877,7057,50177,14401,

%U 32401,8101,14401,24337,44101,78401,12101,57601,44101,32401,50177,24337,30977

%N Primes in A258974.

%C These primes are neither sorted nor uniqued. They are listed in the order found in A258974.

%H Robert Price, <a href="/A258977/b258977.txt">Table of n, a(n) for n = 1..1786</a>

%H OEIS Wiki, <a href="https://oeis.org/wiki/Cyclotomic Polynomials at x=n, n! and sigma(n)">Cyclotomic Polynomials at x=n, n! and sigma(n)</a>

%F a(n) = A258974(A258976(n)).

%p with(numtheory): A258977:=n->`if`(isprime(1+sigma(n)^2), 1+sigma(n)^2, NULL): seq(A258977(n), n=1..300); # _Wesley Ivan Hurt_, Jul 09 2015

%t Select[Table[1 + DivisorSigma[1, n]^2, {n, 10000}], PrimeQ]

%t Select[Table[Cyclotomic[4, DivisorSigma[1, n]], {n, 10000}], PrimeQ]

%o (Magma) [m: n in [1..200] | IsPrime(m) where m is 1 + DivisorSigma(1, n)^2]; // _Vincenzo Librandi_, Jun 16 2015

%o (PARI) for(n=1,100,p=1+sigma(n)^2;if(isprime(p),print1(p,", "))) \\ _Derek Orr_, Jun 18 2015

%Y Cf. A000203, A258974, A258976.

%K nonn

%O 1,1

%A _Robert Price_, Jun 15 2015