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

1,1

Links

Table of n, a(n) for n=1..12.

Formula

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

Example

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.

Prog

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

Crossrefs

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

Sequence in context: A187584 A173228 A061190 * A221082 A002006 A230129

Adjacent sequences: A300396 A300397 A300398 * A300400 A300401 A300402

Keyword

nonn,base,more

Author

G. L. Honaker, Jr., Mar 05 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

Status

approved