A379915 a(n) is the deficiency of the odd squarefree semiprime A046388(n), divided by 2.

3, 5, 9, 11, 11, 15, 19, 17, 23, 21, 29, 31, 27, 35, 29, 35, 35, 43, 47, 39, 41, 53, 45, 59, 55, 59, 51, 65, 57, 59, 71, 79, 65, 83, 79, 89, 69, 83, 89, 71, 95, 91, 77, 107, 81, 109, 107, 103, 87, 119, 95, 115, 131, 125, 99, 119, 101, 139, 105, 143, 107, 137, 131

Offset: 1

Author

Hugo Pfoertner, Jan 06 2025

Keywords

• nonn

Links

• Hugo Pfoertner, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000203, A033879, A046388, A379916, A379917.

Programs

PARI

\\ uses function a379915_17 from A379917
a379915_17(300,2)

Formula

a(n) = (2*A046388(n) - sigma(A046388(n)))/2, where sigma is A000203.

a(n) = A033879(A046388(n))/2.