A349669 a(n) is the n-th Sophie Germain prime reduced mod n.

0, 1, 2, 3, 3, 5, 6, 5, 2, 9, 3, 11, 4, 11, 11, 9, 1, 17, 15, 13, 2, 1, 17, 11, 16, 15, 26, 25, 15, 29, 1, 15, 17, 13, 4, 11, 28, 25, 5, 31, 24, 11, 19, 41, 29, 29, 29, 11, 11, 49, 32, 51, 46, 35, 28, 19, 8, 45, 43, 53, 51, 55, 47, 21, 49, 29, 62, 27, 5, 13, 56, 11

Offset

1,3

Links

Karl-Heinz Hofmann, Table of n, a(n) for n = 1..10000

Formula

a(n) = A005384(n) mod n.

a(n) = ((A005385(n) - 1) / 2) mod n.

Mathematica

p = Select[Prime[Range[400]], PrimeQ[2*# + 1] &]; Mod[p, Range[Length[p]]] (* Amiram Eldar, Jan 11 2022 *)

Prog

(Python)
from sympy import isprime
n = 1
for p in range (2, 10000):
     if isprime(p) and isprime(2*p+1):
         print (p % n, end=", ")
         n += 1
(PARI) lista(nn) = my(v=select(p->isprime(2*p+1), primes(nn))); vector(#v, k, v[k] % k); \\ Michel Marcus, Jan 11 2022

Crossrefs

Cf. A005385 (safe primes), A005384 (Sophie Germain primes).

Sequence in context: A301853 A141419 A072451 * A023156 A051599 A207292

Adjacent sequences: A349666 A349667 A349668 * A349670 A349671 A349672

Keyword

nonn

Author

Karl-Heinz Hofmann, Jan 10 2022

Status

approved