A215486 - OEIS

A215486

n - 1 mod phi(n), where phi(n) is Euler's totient function.

0, 0, 0, 1, 0, 1, 0, 3, 2, 1, 0, 3, 0, 1, 6, 7, 0, 5, 0, 3, 8, 1, 0, 7, 4, 1, 8, 3, 0, 5, 0, 15, 12, 1, 10, 11, 0, 1, 14, 7, 0, 5, 0, 3, 20, 1, 0, 15, 6, 9, 18, 3, 0, 17, 14, 7, 20, 1, 0, 11, 0, 1, 26, 31, 16, 5, 0, 3, 24, 21, 0, 23, 0, 1, 34, 3, 16, 5, 0, 15, 26, 1, 0, 11, 20, 1, 30, 7, 0, 17

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

OFFSET

1,8

COMMENTS

Lehmer conjectured that a(n) = 0 only when n is 1 or prime.

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Wikipedia, Lehmer's totient problem

EXAMPLE

a(8) = 3 because 8 - 1 mod phi(8) = 3.

a(9) = 2 because 9 - 1 mod phi(9) = 2.

a(10) = 1 because 10 - 1 mod phi(10) = 1.