A258974 -id:A258974 - cp's OEIS frontend

A258977 Primes in A258974.

2, 17, 37, 197, 577, 577, 401, 1297, 577, 1601, 3137, 2917, 3137, 8101, 7057, 15377, 2917, 14401, 14401, 8101, 7057, 15877, 5477, 15377, 15877, 7057, 50177, 14401, 32401, 8101, 14401, 24337, 44101, 78401, 12101, 57601, 44101, 32401, 50177, 24337, 30977

Offset: 1

Robert Price, Jun 15 2015

nonn

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

Robert Price, Table of n, a(n) for n = 1..1786
OEIS Wiki, Cyclotomic Polynomials at x=n, n! and sigma(n)

Cf. A000203, A258974, A258976.

[m: n in [1..200] | IsPrime(m) where m is 1 + DivisorSigma(1, n)^2]; // Vincenzo Librandi, Jun 16 2015

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

Select[Table[1 + DivisorSigma[1, n]^2, {n, 10000}], PrimeQ]
Select[Table[Cyclotomic[4, DivisorSigma[1, n]], {n, 10000}], PrimeQ]

for(n=1,100,p=1+sigma(n)^2;if(isprime(p),print1(p,", "))) \\ Derek Orr, Jun 18 2015

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

A258976 Numbers n such that 1 + sigma(n)^2 is prime.

Original entry on oeis.org

1, 3, 5, 13, 14, 15, 19, 22, 23, 27, 28, 34, 39, 40, 44, 48, 53, 54, 56, 58, 65, 68, 73, 75, 82, 83, 84, 87, 88, 89, 95, 99, 104, 108, 109, 114, 116, 118, 124, 125, 129, 133, 134, 135, 136, 145, 149, 152, 158, 171, 177, 178, 179, 186, 202, 203, 209, 210, 215

Offset: 1

Robert Price, Jun 15 2015

nonn

Robert Price, Table of n, a(n) for n = 1..1786
OEIS Wiki, Cyclotomic Polynomials at x=n, n! and sigma(n)

Cf. A000203, A258974, A258977.

[n: n in [1..250] | IsPrime(1 + DivisorSigma(1, n)^2)]; // Vincenzo Librandi, Jun 16 2015

with(numtheory): A258976:=n->`if`(isprime(1+sigma(n)^2), n, NULL): seq(A258976(n), n=1..500); # Wesley Ivan Hurt, Jul 09 2015

Select[ Range[10000], PrimeQ[ 1 + DivisorSigma[1, #]^2] & ]
Select[ Range[10000], PrimeQ[ Cyclotomic[4, DivisorSigma[1, #]]] &]

lista(nn) = for (n=1, nn, if (isprime(1+sigma(n)^2), print1(n, ", "))); \\ Michel Marcus, Jun 17 2015

cp's OEIS Frontend

A258977 Primes in A258974.

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