A098873 - OEIS

A098873

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

1, 1, 2, 1, 1, 1, 1, 4, 1, 5, 1, 34, 7, 1, 1, 1, 2, 2, 1, 1, 1, 1, 4, 24, 8, 1, 10, 7, 1, 1, 2, 1, 3, 2, 1, 1, 1, 2, 1, 1, 1, 1, 28, 5, 2, 2484, 1, 2, 1, 1

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..50.

EXAMPLE

2*((6*1)^1) - 1 = 11 prime, so a(1)=1

2*((6*2)^1) - 1 = 23 prime, so a(2)=1

2*((6*3)^1) - 1 = 35 = 5*7

2*((6*3)^2) - 1 = 647 prime, so a(3)=2

MATHEMATICA

lk[n_]:=Module[{k=1}, While[!PrimeQ[2((6n)^k)-1], k++]; k]; Array[lk, 50] (* Harvey P. Dale, Apr 02 2018 *)

CROSSREFS

Sequence in context: A376267 A060097 A098120 * A377063 A257462 A337131

Adjacent sequences: A098870 A098871 A098872 * A098874 A098875 A098876

KEYWORD

nonn

AUTHOR

Pierre CAMI, Oct 13 2004

EXTENSIONS

Corrected by Harvey P. Dale, Apr 02 2018

STATUS

approved