A340767 Number of primes p <= 6*n + 5 that are congruent to 2 modulo 3.

2, 3, 4, 5, 6, 6, 7, 8, 9, 10, 10, 11, 11, 12, 13, 13, 14, 15, 16, 16, 16, 17, 18, 18, 19, 19, 19, 20, 21, 22, 22, 23, 24, 24, 24, 24, 24, 25, 26, 27, 27, 28, 29, 30, 31, 31, 32, 32, 33, 33, 33, 34, 35, 35, 35, 35, 35, 36, 37, 38, 38, 38, 38, 39, 40, 40, 41, 41, 41, 42, 42

Offset: 0

Author

Jianing Song, Apr 28 2021

Keywords

• nonn
• easy

Examples

			There are 14 primes <= 6*16+5 = 101 that are congruent to 2 modulo 3, namely 2, 5, 11, 17, 23, 29, 41, 47, 53, 59, 71, 83, 89, 101, so a(16) = 14.
		

Links

• Jianing Song, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A003627, A167020, A340764, A172104, A296021, A296020.

Programs

PARI

a(n) = sum(i=1, 6*n+5, isprime(i) && (i%3==2))

Formula

a(n) = A340764(6*n+5).

a(n) = 1 + Sum_{k=0..n+1} A167020(k).