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A231572 Composite numbers n such that lambda(n) divides 5n-5, where lambda is the Carmichael lambda function (A002322). 4
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified February 26 21:48 EST 2020. Contains 332295 sequences. (Running on oeis4.)