A062774 Inverse Moebius transform of PrimePi function.

0, 1, 2, 3, 3, 6, 4, 7, 6, 8, 5, 13, 6, 11, 11, 13, 7, 17, 8, 18, 14, 14, 9, 26, 12, 16, 15, 22, 10, 29, 11, 24, 18, 19, 18, 35, 12, 21, 20, 34, 13, 37, 14, 30, 29, 24, 15, 47, 19, 32, 24, 33, 16, 42, 24, 42, 26, 27, 17, 61, 18, 30, 36, 42, 27, 48, 19, 40, 30, 48, 20, 68, 21, 34

Offset: 1

Author

Labos Elemer, Jul 18 2001

Keywords

• nonn

Examples

			n = 12: divisors = D(12) = {1,2,3,4,6,12}, pi(D(12)) = {0,1,2,2,3,5} of which the sum is 0+1+2+2+3+5 = 13 so a(12) = 13; a(p(n)) = 0+n = n, for n-th prime p(n).
		

Links

• Harry J. Smith, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000720, A007444, A007445.

Programs

PARI

{ for (n=1, 1000, d=divisors(n); write("b062774.txt", n, " ", sum(k=1, length(d), primepi(d[k]))) ) } \\ Harry J. Smith, Aug 10 2009

Formula

a(n) = Sum_{d|n} pi(d).

G.f.: Sum_{k>=1} pi(k)*x^k/(1 - x^k), where pi(k) is the number of primes <= k (A000720). - Ilya Gutkovskiy, Jan 16 2017

a(n) = Sum_{d|n} omega(d!). - Wesley Ivan Hurt, May 23 2021

Extensions

Offset changed from 0 to 1 by Harry J. Smith, Aug 10 2009