A054023 Chowla function of n is not divisible by the number of divisors of n.

4, 6, 8, 10, 12, 14, 16, 18, 20, 21, 22, 24, 25, 26, 28, 30, 33, 34, 38, 40, 42, 44, 45, 46, 48, 49, 52, 54, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 74, 76, 77, 78, 80, 81, 82, 84, 85, 86, 88, 90, 92, 93, 94, 96, 99, 100, 102, 104, 105, 106, 108, 110, 112, 114

Offset

1,1

Comments

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

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Maple

with(numtheory):
[seq(`if`((sigma(i)-i-1) mod tau(i) <> 0, i, print( )), i=1..1000)];

Mathematica

cfQ[n_]:=!Divisible[DivisorSigma[1, n]-1-n, DivisorSigma[0, n]]; Select[ Range[ 150], cfQ] (* Harvey P. Dale, Jul 22 2014 *)

Crossrefs

Complement is A054022.

Cf. A000005, A048050, A054014.

Sequence in context: A176235 A201221 A185604 * A330948 A324705 A032583

Adjacent sequences: A054020 A054021 A054022 * A054024 A054025 A054026

Keyword

nonn

Author

Asher Auel, Jan 19 2000

Status

approved