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A173695 n such that lambda(n) = lambda(n+1). 2
1, 3, 15, 90, 104, 495, 665, 702, 740, 836, 975, 1628, 2625, 2834, 2849, 3800, 7384, 12402, 12560, 13050, 15250, 16470, 22935, 25928, 26274, 29574, 29890, 32864, 39524, 41451, 44286, 47519, 48326, 48704, 48872, 49050 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Lambda(n) is the Carmichael lambda function(A002322).

For n>3 in the sequence, n and n+1 are both composite. - Robert Israel, Oct 31 2016

LINKS

Robert Israel, Table of n, a(n) for n = 1..372

EXAMPLE

104 is in the sequence because lambda(104) = lambda(105) = 12.

MAPLE

with(numtheory):for n from 1 to 50000 do:if lambda(n)=lambda(n+1)then printf(`%d,

  `, n):else fi:od:

CROSSREFS

Cf. A002322.

Sequence in context: A074541 A074550 A205576 * A255688 A025748 A097188

Adjacent sequences:  A173692 A173693 A173694 * A173696 A173697 A173698

KEYWORD

nonn

AUTHOR

Michel Lagneau, Nov 25 2010

STATUS

approved

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Last modified December 14 15:01 EST 2019. Contains 329979 sequences. (Running on oeis4.)