1,5

Seiichi Manyama, Table of n, a(n) for n = 1..10000

(PARI) a(n) = sum(i=1, n, numdiv(i*n)==4); \\ Michel Marcus, Nov 11 2020

tau is A000005.

For tau(i*n) = 2, 3, 6, see A010051, A296084, A338714.

Inspired by A333995.

Sequence in context: A320077 A325522 A006083 * A080301 A326674 A331184

Adjacent sequences: A338710 A338711 A338712 * A338714 A338715 A338716

nonn

N. J. A. Sloane, Nov 11 2020

approved