A152679 Even members of A000203, divided by 2.

2, 3, 6, 4, 9, 6, 14, 7, 12, 12, 9, 10, 21, 16, 18, 12, 30, 21, 20, 28, 15, 36, 16, 24, 27, 24, 19, 30, 28, 45, 21, 48, 22, 42, 39, 36, 24, 62, 36, 49, 27, 60, 36, 60, 40, 45, 30, 84, 31, 48, 52, 42, 72, 34, 63, 48, 72

Offset: 1

Author

Omar E. Pol, Dec 10 2008

Keywords

• easy
• nonn

Links

• Ivan Neretin, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000203, A152677, A152678.

Programs

Mathematica

Select[Table[DivisorSigma[1, n]/2, {n, 1, 70}], IntegerQ](* Ivan Neretin, May 09 2015 *)

PARI

list(lim) = select(x -> denominator(x) == 1, vector(lim, i, sigma(i)/2)); \\ Amiram Eldar, Dec 26 2024

Formula

a(n) = A152678(n)/2.