A054021 Numbers n such that Chowla's function of n is divisible by the number of proper divisors of n.

2, 3, 4, 5, 7, 8, 11, 12, 13, 14, 17, 18, 19, 23, 24, 26, 27, 29, 31, 32, 35, 37, 38, 40, 41, 43, 47, 52, 53, 56, 59, 61, 62, 63, 65, 66, 67, 71, 73, 74, 77, 79, 83, 86, 88, 89, 90, 92, 95, 97, 101, 103, 104, 107, 109, 110, 112, 113, 119, 122, 125, 127, 128, 131, 134, 136

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..1000)];

Mathematica

Select[Range[2, 150], Divisible[DivisorSigma[1, #]-1-#, DivisorSigma[ 0, #]-1]&] (* Harvey P. Dale, Aug 13 2018 *)

Crossrefs

Complement is A054020.

Cf. A032741, A048050, A054015.

Sequence in context: A214036 A100289 A255130 * A066191 A166159 A169693

Adjacent sequences: A054018 A054019 A054020 * A054022 A054023 A054024

Keyword

nonn

Author

Asher Auel, Jan 19 2000

Status

approved