A122132 - OEIS

A122132

Squarefree numbers multiplied by binary powers.

1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23, 24, 26, 28, 29, 30, 31, 32, 33, 34, 35, 37, 38, 39, 40, 41, 42, 43, 44, 46, 47, 48, 51, 52, 53, 55, 56, 57, 58, 59, 60, 61, 62, 64, 65, 66, 67, 68, 69, 70, 71, 73, 74, 76, 77, 78, 79, 80, 82, 83, 84, 85

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

These numbers are called "oddly squarefree" in Banks and Luca. - Michel Marcus, Mar 14 2016

The asymptotic density of this sequence is 8/Pi^2 (A217739). - Amiram Eldar, Sep 21 2020

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

William D. Banks and Florian Luca, Roughly squarefree values of the Euler and Carmichael functions, Acta Arithmetica, Vol. 120, No. 3 (2005), pp. 211-230.

FORMULA

a(n) = A007947(a(n)) * A006519(a(n)) / (2 - a(n) mod 2);

A007947(a(n)) = A000265(a(n)) * (2 - a(n) mod 2).