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

1,1

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.

Links

Table of n, a(n) for n=1..36.

Mathematica

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

Prog

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

Crossrefs

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

Sequence in context: A342184 A247178 A053183 * A026318 A331960 A061204

Adjacent sequences: A247952 A247953 A247954 * A247956 A247957 A247958

Keyword

nonn

Author

Jaroslav Krizek, Sep 28 2014

Extensions

More terms from Michel Marcus, Oct 02 2014

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

Status

approved