A306573 Numbers k such that 11^(k+7) + 7^(k+5) + 5^(k+3) + 3^(k+2) + 2^(k+1) + 1 is prime.

3, 5, 7, 81, 185, 254, 623, 1087, 2407, 7862, 8721, 9353, 13154

Offset

1,1

Comments

a(14) > 41000. - Michael S. Branicky, Mar 25 2023

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