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A173600 Numbers k such that lambda(k) = tau(k). 1
1, 3, 10, 15, 18, 28, 63, 90, 140, 156, 234, 260, 315, 364, 408, 510, 528, 585, 672, 680, 684, 819, 880, 1120, 1248, 1920, 2080, 2912, 3420, 6120, 6528, 6660, 7140, 7920, 8400, 8568, 8892, 9324, 9840, 10710, 10880, 11088, 11424, 13260 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Lambda(n) is the Carmichael lambda function(A002322). tau(n) or sigma_0(n)), the number of divisors of n (A000005).

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..1000

EXAMPLE

2912 is in the sequence because lambda(2912) = tau(2912) = 24.

MAPLE

with(numtheory):for n from 1 to 15000 do: if lambda(n)=tau(n) then printf(`%d,

  `, n):else fi:od:

MATHEMATICA

Select[Range[10^4], CarmichaelLambda[#] == DivisorSigma[0, #] &] (* Amiram Eldar, Jul 15 2019 *)

CROSSREFS

Cf. A000005, A002322.

Sequence in context: A226101 A141463 A134102 * A328987 A108770 A112355

Adjacent sequences:  A173597 A173598 A173599 * A173601 A173602 A173603

KEYWORD

nonn

AUTHOR

Michel Lagneau, Nov 23 2010

STATUS

approved

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Last modified October 21 23:34 EDT 2021. Contains 348160 sequences. (Running on oeis4.)