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A299378 Numbers k such that k * 15^k - 1 is prime. 9
2, 10, 14, 2312, 16718, 26906, 27512, 41260, 45432, 162454, 217606 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(12) > 500000.

LINKS

Table of n, a(n) for n=1..11.

Steven Harvey, Generalized Woodall Search

Wikipedia, Woodall number

MATHEMATICA

Select[Range[1, 10000], PrimeQ[n*15^n-1] &]

PROG

(PARI) for(n=1, 10000, if(isprime(n*15^n-1)), print1(n, ", ")))

(MAGMA) [n: n in [1..10000] |IsPrime(n*15^n-1)]

CROSSREFS

Numbers n such that n * b^n - 1 is prime: A008864 (b=1), A002234 (b=2), A006553 (b=3), A086661 (b=4), A059676 (b=5), A059675 (b=6), A242200 (b=7), A242201 (b=8), A242202 (b=9), A059671 (b=10), A299374 (b=11), A299375 (b=12), A299376 (b=13), A299377 (b=14), this sequence (b=15), A299379 (b=16), A299380 (b=17), A299381 (b=18), A299382 (b=19), A299383 (b=20).

Sequence in context: A244268 A233454 A065989 * A031222 A272041 A212160

Adjacent sequences:  A299375 A299376 A299377 * A299379 A299380 A299381

KEYWORD

nonn,more,hard

AUTHOR

Tim Johannes Ohrtmann, Feb 08 2018

STATUS

approved

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Last modified September 26 05:07 EDT 2021. Contains 347664 sequences. (Running on oeis4.)