A025472 a(n) is the position of 7^n among the powers of primes (A000961).

1, 6, 24, 87, 393, 2002, 11212, 65907, 398221, 2454882, 15355483, 97168563, 620657849, 3995177593, 25885249943, 168651040452, 1104127513216, 7259026757936, 47901525960522, 317140345586299, 2105877518905780, 14020561598521781, 93570332415595735, 625829903112713938

Offset

0,2

Comments

The number of prime powers <= 7^n. - Robert G. Wilson v, Dec 16 2019

Links

Table of n, a(n) for n=0..23.

Formula

a(n) = A065515(7^n). - Michel Marcus, Mar 24 2013

Prog

(PARI) a(n)= n=7^n+.5; 1+sum(k=1, log(n)\log(2), primepi(n^(1/k))) \\ Michel Marcus, Mar 25 2013

Crossrefs

Cf. A000420 (7^n), A000961, A065515.

Sequence in context: A124807 A271789 A121532 * A255474 A249976 A181618

Adjacent sequences: A025469 A025470 A025471 * A025473 A025474 A025475

Keyword

nonn

Author

Clark Kimberling

Extensions

a(11)-a(17) from Robert G. Wilson v, Dec 13 2019

a(18)-a(22) from Daniel Suteu, Dec 15 2019

a(23) from Robert G. Wilson v, Dec 15 2019

Status

approved