A152145 a(n) = least k such that 3*k*2^n-1 or 3*k*2^n+1 (or both) is prime.

1, 1, 1, 1, 1, 1, 1, 1, 1, 4, 2, 1, 1, 3, 3, 3, 4, 2, 1, 9, 6, 3, 9, 15, 13, 11, 9, 5, 4, 2, 1, 5, 4, 2, 1, 2, 1, 2, 1, 4, 2, 1, 2, 1, 5, 18, 9, 9, 5, 18, 9, 7, 8, 4, 2, 1, 9, 17, 18, 9, 15

Offset

0,10

Links

Pierre CAMI, Table of n, a(n) for n = 0..1230

Mathematica

lk[n_]:=Module[{k=1}, While[NoneTrue[3*k*2^n+{1, -1}, PrimeQ], k++]; k]; Array[ lk, 70, 0] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 03 2019 *)

Crossrefs

A152141

Sequence in context: A097526 A051149 A293424 * A288251 A024553 A051758

Adjacent sequences: A152142 A152143 A152144 * A152146 A152147 A152148

Keyword

nonn

Author

Pierre CAMI, Nov 26 2008, Nov 27 2008

Status

approved