A098872 - OEIS

A098872

Least k such that 2*((6*n)^k) + 1 is prime.

1, 3, 1, 2, 1, 1, 2, 1, 1, 3, 2, 2, 1, 4, 1, 1, 2, 5, 1, 1, 4, 2, 1, 5, 3, 1, 2, 1, 1, 8, 1, 3, 1, 1, 1, 1, 66, 1, 6, 2, 3, 3, 5, 2, 1, 4, 7, 1, 9, 1, 1, 3, 6, 2, 1, 1, 96, 4, 1, 2, 1, 62, 1, 1, 9, 5, 159, 4, 1, 7, 1, 4, 1, 8, 2, 2, 2, 1, 2, 8, 2, 2, 1, 1, 1, 1, 54, 8, 1, 5, 1, 16, 1, 1, 2, 1, 7, 2, 4, 1, 1

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..101.

EXAMPLE

2*((6*1)^1) + 1 = 13 prime, so a(1)=1

2*((6*2)^1) + 1 = 25 = 5^2

2*((6*2)^2) + 1 = 289 = 17^2

2*((6*2)^3) + 1 = 3457 prime, so a(2)=3

MATHEMATICA

lk[n_]:=Module[{k=1}, While[!PrimeQ[2(6n)^k+1], k++]; k]; Array[lk, 110] (* Harvey P. Dale, May 16 2012 *)

CROSSREFS

Sequence in context: A377514 A016569 A072801 * A349473 A167366 A139436

Adjacent sequences: A098869 A098870 A098871 * A098873 A098874 A098875

KEYWORD

nonn

AUTHOR

Pierre CAMI, Oct 13 2004

EXTENSIONS

Extended by R. J. Mathar, Nov 13 2009

STATUS

approved