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A306573 Numbers k such that 11^(k+7) + 7^(k+5) + 5^(k+3) + 3^(k+2) + 2^(k+1) + 1 is prime. 2
3, 5, 7, 81, 185, 254, 623, 1087, 2407, 7862, 8721, 9353, 13154 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..13.

MATHEMATICA

ParallelMap[If[PrimeQ[11^(#+7) + 7^(#+5) + 5^(#+3) + 3^(#+2) + 2^(#+1) + 1], #, Nothing] &, Range@8000]

PROG

(PARI) is(n) = ispseudoprime(11^(n+7) + 7^(n+5) + 5^(n+3) + 3^(n+2) + 2^(n+1) + 1) \\ Felix Fröhlich, Mar 06 2019

CROSSREFS

Sequence in context: A291438 A056145 A119939 * A254925 A153138 A201270

Adjacent sequences:  A306570 A306571 A306572 * A306574 A306575 A306576

KEYWORD

nonn,more,hard

AUTHOR

Mikk Heidemaa, Feb 24 2019

STATUS

approved

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Last modified October 28 13:26 EDT 2020. Contains 338055 sequences. (Running on oeis4.)