A306996 Number of primes q < prime(n), such that 4*prime(n) + q is prime.

0, 0, 1, 1, 1, 1, 3, 3, 3, 2, 3, 3, 3, 2, 5, 3, 4, 4, 3, 4, 3, 5, 4, 7, 6, 6, 7, 6, 7, 5, 4, 7, 7, 9, 9, 8, 5, 5, 8, 7, 11, 9, 7, 6, 7, 8, 10, 9, 10, 10, 9, 11, 11, 13, 10, 11, 9, 13, 9, 11, 10, 10, 12, 9, 12, 12, 13, 11, 13, 16, 15, 19, 11, 11, 13, 13, 17, 9, 19, 12, 14, 12, 15, 16, 15, 18, 13, 17, 16, 12, 15, 15, 12, 16, 17

Offset

1,7

Comments

Conjecture: a(n) > 0 for all n >= 3. - Dmitry Kamenetsky, Mar 18 2019

Links

Ashaz Jameel, Table of n, a(n) for n = 1..10000

Prog

(PARI) a(n) = my(s=0, p=prime(n)); forprime(q=1, p-1, s += isprime(4*p+q)); s; \\ Michel Marcus, Mar 26 2026

Crossrefs

Cf. A306995, A306997.

Sequence in context: A259494 A356525 A226895 * A166007 A372748 A087497

Adjacent sequences: A306993 A306994 A306995 * A306997 A306998 A306999

Keyword

nonn

Author

Dmitry Kamenetsky, Mar 18 2019

Status

approved