A300399 a(n) = number of primes that end in 7 among the first 10^n primes.

2, 24, 254, 2508, 25015, 250014, 2500283, 25000402, 250002505, 2500005319, 25000014226, 250000051446

Offset: 1

Author

G. L. Honaker, Jr., Mar 05 2018

Keywords

• nonn
• base
• more

Examples

			a(1) = 2 because the first 10 primes are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, among which there are two primes ending in 7.
		

Crossrefs

Cf. A006988, A030432, A185714, A300397, A300398, A300400.

Programs

PARI

a(n) = #select(x->((x % 10) == 7), primes(10^n)); \\ Michel Marcus, Mar 07 2018

Formula

a(n) = A185714(A006988(n)). - Michel Marcus, Mar 20 2018

Extensions

a(3)-a(8) from Chuck Gaydos

a(9) from Jon E. Schoenfield, Mar 20 2018

a(10)-a(12) from Giovanni Resta, Mar 27 2018