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A297361 Numbers n such that (3^lambda(n) - 1)/n is prime, where lambda(n) is the Carmichael lambda function (A002322). 0
4, 16, 40, 56, 160, 7280 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The corresponding primes are 2, 5, 2, 13, 41, 73.

LINKS

Table of n, a(n) for n=1..6.

EXAMPLE

4 is in the sequence since lambda(4) = 2 and (3^2 - 1)/4 = 2 is prime.

MATHEMATICA

aQ[n_] := PrimeQ[(3^CarmichaelLambda[n]-1)/n]; a={}; Do[If[aQ[k], AppendTo[a, k]], {k, 1, 10000}]; a

PROG

(PARI) isok(n) = (denominator(p=(3^lcm(znstar(n)[2])-1)/n)==1) && isprime(p); \\ Michel Marcus, Dec 29 2017

CROSSREFS

Cf. A002322.

Sequence in context: A103770 A121318 A152133 * A210440 A220499 A110477

Adjacent sequences:  A297358 A297359 A297360 * A297362 A297363 A297364

KEYWORD

nonn,more

AUTHOR

Amiram Eldar, Dec 29 2017

STATUS

approved

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Last modified May 26 05:25 EDT 2019. Contains 323579 sequences. (Running on oeis4.)