A138067 Least k > 1 such that (2n-1)^k + 2 is prime, or 0 if no such number exists.

2, 2, 3, 0, 2, 5, 0, 2, 105, 0, 2, 11, 0, 5, 3, 0, 2, 15, 0, 2, 9, 0, 2, 113, 0, 5, 7, 0, 2, 27, 0, 3, 3, 0, 3, 3, 0, 12, 61, 0, 2, 3, 0, 4, 255, 0, 8, 63, 0, 2, 9, 0, 2, 3473, 0, 2, 3, 0, 2, 15, 0, 2, 87, 0, 3, 23, 0, 36, 1861, 0, 4, 3, 0, 2, 5, 0, 3, 7, 0, 136, 425, 0, 11

Offset

1,1

Comments

a(3n+1) = 0 for n > 0.

a(84) > 100000. - Ray Chandler, Aug 10 2011

Links

Table of n, a(n) for n=1..83.

Crossrefs

Cf. A084713 (smallest prime of the form (2n-1)^k + 2, or 0 if no such number exists).

Cf. A138066 (least k > 0 such that (2n-1)^k + 2 is prime, or 0 if no such number exists).

Cf. A051783 (k such that 3^k + 2 is prime).

Cf. A087885 (k such that 5^k + 2 is prime).

Cf. A090649, A109076, A113480, A138048, A138049, A138050, A138051, A087886, A113481.

Sequence in context: A307356 A091426 A053761 * A324348 A125093 A294898

Adjacent sequences: A138064 A138065 A138066 * A138068 A138069 A138070

Keyword

hard,nonn

Author

Alexander Adamchuk, Mar 02 2008

Extensions

a(54)-a(83) from Donovan Johnson, Oct 29 2008

Status

approved