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A339862 Primes p such that p + sigma(p-1) is prime. 3
2, 7, 11, 13, 23, 31, 41, 43, 53, 59, 61, 67, 89, 97, 107, 109, 127, 131, 151, 167, 179, 181, 193, 211, 227, 233, 251, 263, 271, 283, 293, 307, 311, 313, 317, 353, 397, 409, 431, 439, 457, 487, 503, 523, 541, 563, 571, 599, 607, 613, 619, 631, 653, 659, 661, 673, 701, 709, 739, 743, 773, 787, 809 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

EXAMPLE

a(3)=11 is a term because 11 is prime, sigma(11-1)=1+2+5+10=18, and 11+18=29 is prime.

MAPLE

select(t -> isprime(t) and isprime(t+numtheory:-sigma(t-1)), [2, seq(i, i=3..1000, 2)]);

CROSSREFS

Cf. A000203.

Sequence in context: A019346 A045369 A157975 * A045370 A117048 A040128

Adjacent sequences:  A339859 A339860 A339861 * A339863 A339864 A339865

KEYWORD

nonn

AUTHOR

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

STATUS

approved

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Last modified July 4 12:28 EDT 2022. Contains 355075 sequences. (Running on oeis4.)