A258430 Primes in A088580.

2, 5, 7, 13, 19, 13, 29, 19, 43, 37, 61, 43, 41, 31, 73, 61, 43, 97, 79, 73, 73, 73, 61, 97, 127, 97, 73, 97, 127, 109, 181, 113, 157, 103, 211, 193, 163, 109, 281, 241, 211, 181, 157, 313, 337, 241, 271, 139, 337, 193, 181, 223, 229, 151, 373, 193, 241, 379

Offset: 1

Author

Robert Price, May 29 2015

Keywords

• nonn

Comments

These primes are neither sorted nor uniqued. They are listed in the order found in A088580.

Links

• Robert Price, Table of n, a(n) for n = 1..2967
• OEIS Wiki, Cyclotomic Polynomials at x=n, n! and sigma(n)

Crossrefs

Cf. A088580, A065512.

Programs

Magma

[a: n in [1..300] | IsPrime(a) where a is 1 + SumOfDivisors(n)]; // Vincenzo Librandi, May 30 2015

Maple

with(numtheory): A258430:=n->`if`(isprime(1+sigma(n)), 1+sigma(n), NULL): seq(A258430(n), n=1..300); # Wesley Ivan Hurt, Jul 09 2015

Mathematica

Select[Table[1 + DivisorSigma[1, n], {n, 10000}], PrimeQ]

PARI

select(x->isprime(x), vector(200, n, 1+sigma(n))) \\ Michel Marcus, Jun 04 2015

Formula

a(n) = A088580(A065512(n)). - Michel Marcus, Jun 04 2015