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A125609
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Smallest prime p such that 3^n divides p^2 - 1.
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22
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2, 17, 53, 163, 487, 1459, 4373, 13121, 39367, 472391, 1062881, 1062881, 19131877, 19131877, 57395627, 86093443, 258280327, 3874204891, 6973568801, 6973568801, 188286357653, 188286357653, 188286357653, 4518872583697, 15251194969973
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OFFSET
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1,1
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COMMENTS
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Smallest prime of the form k*3^n-1 or k*3^n+1. - Robert Israel, Oct 27 2019
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LINKS
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MAPLE
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f:= proc(n) local k;
for k from 1 do
if isprime(k*3^n-1) then return k*3^n-1
elif isprime(k*3^n+1) then return k*3^n+1
fi
od
end proc:
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MATHEMATICA
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f[n_] := Module[{k}, For[k = 1, True, k++, If[PrimeQ[k*3^n-1], Return[k*3^n-1], If[PrimeQ[k*3^n+1], Return[k*3^n+1]]]]];
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PROG
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For PARI program see link.
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CROSSREFS
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Cf. A125609 = Smallest prime p such that 3^n divides p^2 - 1. Cf. A125610 = Smallest prime p such that 5^n divides p^4 - 1. Cf. A125611 = Smallest prime p such that 7^n divides p^6 - 1. Cf. A125612 = Smallest prime p such that 11^n divides p^10 - 1. Cf. A125632 = Smallest prime p such that 13^n divides p^12 - 1. Cf. A125633 = Smallest prime p such that 17^n divides p^16 - 1. Cf. A125634 = Smallest prime p such that 19^n divides p^18 - 1. Cf. A125635 = Smallest prime p such that 257^n divides p^256 - 1.
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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