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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 (list; graph; refs; listen; history; text; internal format)
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 k-th 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 (2011).

G. Martin and C. Pomerance, The iterated Carmichael lambda-function and the number of cycles of the power generator", Acta Arith. 118:4 (2005), pp. 305-335.

EXAMPLE

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

MATHEMATICA

Table[CarmichaelLambda[CarmichaelLambda[n]], {n, 1, 100}]

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

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Last modified May 24 17:23 EDT 2017. Contains 286985 sequences.