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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
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
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 *)
PROG
(PARI) isok(n) = numdiv(n) == lcm(znstar(n)[2]) \\ Miles Englezou, Feb 05 2024
CROSSREFS
Sequence in context: A226101 A141463 A134102 * A328987 A108770 A112355
KEYWORD
nonn
AUTHOR
Michel Lagneau, Nov 23 2010
STATUS
approved