A091374 Number of numbers <= n having fewer prime factors than the value of their smallest prime factor.

1, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13, 14, 14, 14, 14, 15, 15, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 22, 22, 23, 23, 24, 24, 25, 25, 26, 26, 27, 27, 28, 28, 29, 29, 30, 30, 30, 30, 31, 31, 32, 32, 33, 33, 34, 34, 35, 35

Offset: 1

Author

Reinhard Zumkeller, Jan 04 2004

Keywords

• nonn

Comments

a(n) = #{m: A001222(m) < A020639(m), m<=n};

A091372(n) + A091373(n) + a(n) = n.

Crossrefs

Cf. A091377, A091371.

Programs

PARI

isok(n) = {my(f=factor(n)); (#f~ == 0) || (bigomega(n) < f[1,1]);}
a(n) = sum(k=1, n, isok(k)); \\ Michel Marcus, Feb 05 2016