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

1,1

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

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 *)

Crossrefs

Complement is A054021.

Cf. A032741, A048050, A054015.

Sequence in context: A328244 A037198 A359277 * A121014 A153519 A020219

Adjacent sequences: A054017 A054018 A054019 * A054021 A054022 A054023

Keyword

nonn

Author

Asher Auel, Jan 19 2000

Status

approved