A231573 Composite numbers n such that lambda(n) divides 6n-6, where lambda is the Carmichael lambda function (A002322).

4, 6, 8, 9, 12, 14, 15, 18, 21, 24, 28, 35, 36, 39, 42, 45, 56, 63, 65, 66, 72, 76, 84, 91, 105, 117, 126, 133, 153, 168, 186, 195, 231, 247, 252, 259, 273, 276, 315, 341, 344, 396, 435, 455, 481, 504, 532, 561, 585, 616, 645, 651, 671, 703, 804, 819, 861

Offset

1,1

Comments

Contains the Carmichael numbers, A231569 and A231570.

Conjecture: the relative asymptotic density of Carmichael numbers in this sequence exists, is positive and smaller than 1.

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

J. M. Grau and Antonio Oller-Marcén, Generalizing Giuga's conjecture, arXiv:1103.3483 [math.NT], 2011.

Mathematica

Select [1 + Range[100000], ! PrimeQ[#] && IntegerQ[6 (# -1)/ CarmichaelLambda[#]] &]

Prog

(PARI) is(n)=!isprime(n) && (6*n-6)%lcm(znstar(n)[2])==0 && n>1 \\ Charles R Greathouse IV, Nov 13 2013

Crossrefs

Cf. A231569-A231575, A002322.

Sequence in context: A211771 A211772 A353355 * A327204 A047409 A161576

Adjacent sequences: A231570 A231571 A231572 * A231574 A231575 A231576

Keyword

nonn

Author

José María Grau Ribas, Nov 11 2013

Status

approved