A054020 Chowla's function of n is not divisible by the number of proper divisors of n.

6, 9, 10, 15, 16, 20, 21, 22, 25, 28, 30, 33, 34, 36, 39, 42, 44, 45, 46, 48, 49, 50, 51, 54, 55, 57, 58, 60, 64, 68, 69, 70, 72, 75, 76, 78, 80, 81, 82, 84, 85, 87, 91, 93, 94, 96, 98, 99, 100, 102, 105, 106, 108, 111, 114, 115, 116, 117, 118, 120, 121, 123, 124, 126

Offset: 1

Author

Asher Auel, Jan 19 2000

Keywords

• nonn

Comments

Chowla's function (A048050) = sum of divisors of n except 1 and n.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Complement is A054021.

Cf. A032741, A048050, A054015.

Programs

Maple

with(numtheory):
[seq(`if`((sigma(i)-i-1) mod (tau(i)-1) <> 0,i,print( )),i=2..500)];

Mathematica

Select[Range[2,150],!Divisible[DivisorSigma[1,#]-#-1,DivisorSigma[ 0,#]- 1]&] (* Harvey P. Dale, May 27 2014 *)