

A181776


a(n) = lambda(lambda(n)), where lambda(n) is the Carmichael lambda function (A002322).


1



1, 1, 1, 1, 2, 1, 2, 1, 2, 2, 4, 1, 2, 2, 2, 2, 4, 2, 6, 2, 2, 4, 10, 1, 4, 2, 6, 2, 6, 2, 4, 2, 4, 4, 2, 2, 6, 6, 2, 2, 4, 2, 6, 4, 2, 10, 22, 2, 6, 4, 4, 2, 12, 6, 4, 2, 6, 6, 28, 2, 4, 4, 2, 4, 2, 4, 10, 4, 10, 2, 12, 2, 6, 6, 4, 6, 4, 2, 12, 2, 18, 4, 40, 2, 4, 6, 6
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OFFSET

1,5


COMMENTS

Harland proves the conjecture of Martin & Pomerance that a(n) = n exp ((1 + o(1))(log log n)^2 log log log n) for almost all n, as well as a generalization to kth iterates.  Charles R Greathouse IV, Dec 21 2011


LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
Nick Harland, The iterated Carmichael lambda function, arXiv:1111.3667 [math.NT], 2011.
G. Martin and C. Pomerance, The iterated Carmichael lambdafunction and the number of cycles of the power generator, Acta Arith. 118:4 (2005), pp. 305335.


EXAMPLE

a(11) = 4 is in the sequence because A002322(11) = 10 and A002322(10) = 4.


MATHEMATICA

Table[CarmichaelLambda[CarmichaelLambda[n]], {n, 1, 100}]
Table[Nest[CarmichaelLambda, n, 2], {n, 100}] (* Harvey P. Dale, Jul 01 2020 *)


PROG

(PARI) a(n)=lcm(znstar(lcm(znstar(n)[2]))[2]) \\ Charles R Greathouse IV, Nov 04 2012


CROSSREFS

Cf. A002322, A002997.
Sequence in context: A226516 A002300 A049099 * A243036 A230224 A206941
Adjacent sequences: A181773 A181774 A181775 * A181777 A181778 A181779


KEYWORD

nonn


AUTHOR

Michel Lagneau, Nov 12 2010


STATUS

approved



