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A308553
Numbers k such that 5^(k+3) + 3^(k+2) + 2^(k+1) + 1 is prime.
0
0, 4, 8, 524, 972, 3780, 7704
OFFSET
1,2
COMMENTS
Larger k values yield probable primes.
a(8) > 100000 (if it exists). - Michael S. Branicky, Nov 11 2024
MATHEMATICA
ParallelTable[If[PrimeQ[5^(n+3) + 3^(n+2) + 2^(n+1) + 1], n, Nothing], {n, 0, 10^4}]
CROSSREFS
Cf. A306573.
Sequence in context: A012994 A136386 A260726 * A177860 A013443 A013442
KEYWORD
nonn,hard,more,changed
AUTHOR
Mikk Heidemaa, Jun 07 2019
STATUS
approved