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A113539 a(n) is the minimal k such that 3^n +/- k are primes. 0
2, 4, 2, 14, 10, 26, 8, 80, 20, 20, 110, 64, 8, 16, 110, 106, 10, 280, 8, 166, 92, 364, 68, 310, 130, 836, 70, 364, 238, 434, 892, 1844, 58, 140, 10, 740, 482, 1274, 308, 494, 1220, 2644, 790, 646, 2248, 2456, 422, 314, 1072, 1124, 782, 200, 98, 1826, 1502 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

Table of n, a(n) for n=2..56.

EXAMPLE

First term (at n=2) is a(2)=2 because 3^2 +/- 2 are primes; second term (at n=3) is a(3)=4 because 3^3 +/- 4 are primes.

MATHEMATICA

f[n_] := Block[{k = 2}, While[ !PrimeQ[3^n + k] || !PrimeQ[3^n - k], k += 2]; k]; Table[ f[n], {n, 2, 56}] (* Robert G. Wilson v *)

CROSSREFS

Sequence in context: A153801 A062867 A264027 * A215055 A152877 A071353

Adjacent sequences:  A113536 A113537 A113538 * A113540 A113541 A113542

KEYWORD

nonn

AUTHOR

Zak Seidov, Jan 13 2006

EXTENSIONS

Corrected and extended by Robert G. Wilson v, Jan 18 2006

STATUS

approved

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Last modified December 13 09:57 EST 2019. Contains 329968 sequences. (Running on oeis4.)