A289497 Number of primes in the interval [6n, 7n].

1, 1, 1, 0, 1, 2, 2, 1, 2, 2, 3, 3, 3, 2, 3, 5, 4, 2, 2, 4, 4, 4, 4, 5, 5, 6, 5, 5, 6, 5, 5, 5, 5, 5, 7, 7, 8, 7, 7, 7, 8, 8, 7, 7, 8, 8, 6, 6, 6, 8, 9, 8, 7, 8, 10, 10, 10, 10, 9, 9, 10, 11, 11, 10, 10, 12, 12, 12, 12, 12, 12, 13, 13, 11, 12, 12, 10, 9, 10, 10

Offset: 1

Author

FUNG Cheok Yin, Jul 07 2017

Keywords

• nonn
• easy

Links

• FUNG Cheok Yin, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A035250, A289493, A289494, A289495, A289496, A289498, A289499, A289500.

Programs

PARI

a(n) = primepi(7*n) - primepi(6*n); \\ Michel Marcus, Jul 08 2017