A340763 - OEIS

A340763

Number of primes p <= n that are congruent to 1 modulo 3.

0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10

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OFFSET

1,13

LINKS

Jianing Song, Table of n, a(n) for n = 1..10000

FORMULA

a(n) + A340764(n) = A000720(n) - 1 for n >= 3.

EXAMPLE

There are 11 primes <= 100 that are congruent to 1 modulo 3, namely 7, 13, 19, 31, 37, 43, 61, 67, 73, 79, 97, so a(100) = 11.

PROG

(PARI) a(n) = sum(i=1, n, isprime(i) && (i%3==1))

CROSSREFS