A280710 - OEIS

A280710

Characteristic function of squarefree semiprimes.

0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

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OFFSET

COMMENTS

Möbius transform of A079275(n). [See Oudra formula] - Wesley Ivan Hurt, Jul 10 2025

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for characteristic functions

Index entries for sequences computed from exponents in factorization of n

FORMULA

a(n) = floor(Omega(n)*mu(n)^2/2)*floor(2*mu(n)^2/Omega(n)) for n>1 with a(1) = 0 where Omega(n) = A001222(n) and mu(n) = A008683(n).

a(n) = A008966(n)*A064911(n). - Felix Fröhlich, Jan 07 2017

a(n) = Sum_{d|n} A079275(d)*A008683(n/d). - Ridouane Oudra, Jul 03 2025