A247955 Primes p such that there is prime q with sigma(q+2) = p.

7, 13, 31, 1093, 2801, 5113, 8011, 17293, 30103, 30941, 86143, 459007, 552793, 579883, 732541, 1191373, 3500201, 3730693, 4534771, 5168803, 5333791, 7450171, 10378063, 25646167, 25882657, 28792661, 30266503, 43553401, 48037081, 52265671, 56964757, 62433703, 65504743, 67856407, 76413823, 77572057

Offset: 1

Author

Jaroslav Krizek, Sep 28 2014

Keywords

• nonn

Comments

Primes p such that there is prime q such that A000203(q+2) = p.

Primes p of the form sigma(A171130(n)) in increasing order.

Crossrefs

Cf. A000203, A008438, A171130, A247791, A247820, A247821, A247822, A247823, A247954.

Programs

Mathematica

Sort[Select[DivisorSigma[1,#+2]&/@Prime[Range[5200000]],PrimeQ]] (* Harvey P. Dale, Apr 27 2022 *)

PARI

v=[];forprime(p=1,10^8,if(ispseudoprime(sigma(p+2)),v=concat(v,sigma(p+2))));v \\ Derek Orr, Oct 26 2014

Extensions

More terms from Michel Marcus, Oct 02 2014

Corrected and extended by Harvey P. Dale, Apr 27 2022