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A073803 Number of divisors of n is smaller than that of sigma(n). 7
3, 5, 6, 7, 10, 11, 13, 14, 15, 17, 19, 20, 21, 22, 23, 24, 26, 27, 28, 29, 30, 31, 33, 34, 35, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 49, 51, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71, 73, 74, 76, 77, 78, 79, 82, 83, 85, 86, 87, 88, 89, 91 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

FORMULA

Solutions to A000005(x) < A062068(x)=A000005(A000203(x)).

EXAMPLE

x=96: D[96]={1,2,3,4,6,8,12,16,24,32,48,96},12 divisors; D[sigma(96)]={1,2,3,4,6,7,9,12,14,18,21,28,36,42,63,84,126,252}, 18 divisors; 12<18, so 96 is here.

MAPLE

filter:= proc(n) uses numtheory; tau(n) < tau(sigma(n)) end proc:

select(filter, [$1..100]); # Robert Israel, Aug 03 2020

MATHEMATICA

Do[s=DivisorSigma[0, DivisorSigma[1, n]]; s0=DivisorSigma[0, n]; If[Greater[s0, s], Print[n]], {n, 1, 1000}]

Select[Range[100], DivisorSigma[0, #]<DivisorSigma[0, DivisorSigma[1, #]]&] (* Harvey P. Dale, Sep 22 2019 *)

CROSSREFS

Cf. A000005, A000203, A062068, A073802-A073804, A037197.

Sequence in context: A136806 A253550 A295307 * A336353 A182851 A281995

Adjacent sequences: A073800 A073801 A073802 * A073804 A073805 A073806

KEYWORD

nonn

AUTHOR

Labos Elemer, Aug 13 2002

STATUS

approved

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Last modified February 4 10:27 EST 2023. Contains 360053 sequences. (Running on oeis4.)