A308829 Numbers k such that 3^k - k + 1 is prime.
0, 1, 5, 27, 45, 47, 75, 8895, 11405, 29517, 84615, 218307
Offset: 1
Programs
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Mathematica
ListA[k_] := Block[{seq = {}, n = 0, i = 0}, While[Length[seq] < k, {n = 3^i - i + 1, If[PrimeQ[n], AppendTo[seq, i]], i += 1}]; seq] -
PARI
isok(k) = isprime(3^k - k + 1); \\ Jinyuan Wang, Aug 03 2019
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Sage
def list_a(k): return [i for i in range(k) if (3**i) - i + 1 in Primes()]
Comments