A138048 - OEIS

A138048

Numbers k such that 15^k + 2 is prime.

0, 1, 2, 4, 5, 10, 11, 16, 20, 52, 75, 106, 112, 132, 371, 3264, 3424, 5477, 7516, 10365, 44557, 150706

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OFFSET

1,3

COMMENTS

No further terms < 100000. - Ray Chandler, Aug 05 2011

a(23) > 2*10^5. - Robert Price, Jun 23 2015

LINKS

Henri & Renaud Lifchitz, PRP Records.

MATHEMATICA

Do[ f = 15^n + 2; If[ PrimeQ[ f ], Print[ {n, f} ] ], {n, 1, 371} ]

PROG

(PARI) is(n)=ispseudoprime(15^n+2) \\ Charles R Greathouse IV, Feb 17 2017

CROSSREFS

Cf. A051783 (k such that 3^k + 2 is prime).

Cf. A087885 (k such that 5^k + 2 is prime).

KEYWORD

nonn,more

AUTHOR

EXTENSIONS

a(16)-a(19) from Ray Chandler, Jul 30 2011

a(20) found by Lelio R Paula, Dec 2006

a(21) from Ray Chandler, Jul 31 2011

a(22) from Robert Price, Jun 23 2015

STATUS

approved