A231572 Composite numbers n such that lambda(n) divides 5n-5, where lambda is the Carmichael lambda function (A002322).

25, 33, 165, 217, 325, 385, 561, 793, 825, 1025, 1045, 1065, 1105, 1353, 1525, 1705, 1729, 2465, 2665, 2821, 3565, 4123, 4681, 5005, 5185, 5425, 6601, 6697, 8029, 8569, 8911, 9073, 10585, 11005, 12025, 12505, 12801, 13237, 13741, 14707, 14725, 14905, 15457

Offset

1,1

Comments

Contains the Carmichael numbers (A002997).

Conjecture: the relative asymptotic density of the 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[5 (# -1)/ CarmichaelLambda[#]] &]

Prog

(PARI) is(n)=!isprime(n) && (5*n-5)%lcm(znstar(n)[2])==0 && n>1 \\ Charles R Greathouse IV, Nov 13 2013

Crossrefs

Cf. A231569-A231575, A002322.

Sequence in context: A068411 A020160 A075452 * A020258 A227516 A281369

Adjacent sequences: A231569 A231570 A231571 * A231573 A231574 A231575

Keyword

nonn

Author

José María Grau Ribas, Nov 11 2013

Status

approved