A339864 Primes of the form p + sigma(p-1) for primes p.

3, 19, 29, 41, 59, 103, 131, 139, 151, 149, 229, 211, 269, 349, 269, 389, 439, 383, 523, 419, 449, 727, 701, 787, 569, 683, 719, 659, 991, 859, 811, 1009, 887, 1153, 877, 1109, 1489, 1489, 1223, 1327, 1657, 1579, 1259, 1693, 2221, 1409, 2011, 1607, 1831, 2251, 1867, 2503, 1801, 1811, 2677, 2689

Offset

1,1

Comments

Terms are in order of increasing p.

Terms that occur more than once include 269, 1489, 2903, 3271, 5099, 7159.

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Formula

a(n) = A339862(n) + sigma(A339862(n)-1).

Example

A339862(3) = 11 so a(3) = 11 + sigma(11-1) = 29.

Maple

select(isprime, map(t -> t + numtheory:-sigma(t-1), [seq(ithprime(i), i=1..200)]));

Mathematica

Select[#+DivisorSigma[1, #-1]&/@Prime[Range[200]], PrimeQ] (* Harvey P. Dale, Jan 31 2021 *)

Crossrefs

Cf. A000203, A339882.

Sequence in context: A295322 A296934 A062619 * A180451 A108137 A250027

Adjacent sequences: A339861 A339862 A339863 * A339865 A339866 A339867

Keyword

nonn

Author

J. M. Bergot and Robert Israel, Dec 19 2020

Extensions

Definition clarified by Harvey P. Dale, Jan 31 2021

Status

approved