A027883 Positions of primes in sequence (A246655) of primes and prime powers {p^i, i >= 1}.

1, 2, 4, 5, 8, 9, 11, 12, 13, 16, 17, 19, 20, 21, 22, 24, 25, 26, 28, 29, 30, 31, 33, 34, 35, 36, 37, 38, 39, 40, 43, 45, 46, 47, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 69, 71, 72, 73, 74, 75, 76, 77, 79, 80, 81, 82, 83, 84, 85, 87, 88, 89

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Links

• Ray Chandler, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A024620, A246655.

Programs

Python

from sympy import prime, primepi, integer_nthroot
def A027883(n):
    p = prime(n)
    return n+sum(primepi(integer_nthroot(p,k)[0]) for k in range(2,p.bit_length())) # Chai Wah Wu, Dec 08 2024

Formula

a(n) = A024620(n) - 1.

Extensions

More terms from Erich Friedman.

Name clarified by Ilya Gutkovskiy, Mar 12 2020