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A054023 Chowla function of n is not divisible by the number of divisors of n. 2
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 (list; graph; refs; listen; history; text; internal format)
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 (asher.auel(AT)reed.edu), Jan 19 2000

STATUS

approved

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Last modified October 17 06:07 EDT 2021. Contains 348048 sequences. (Running on oeis4.)