A038699 - OEIS

A038699

Riesel problem: Smallest prime of form n*2^m-1, m >= 0, or 0 if no such prime exists.

3, 3, 2, 3, 19, 5, 13, 7, 17, 19, 43, 11, 103, 13, 29, 31, 67, 17, 37, 19, 41, 43, 367, 23, 199, 103, 53, 223, 463, 29, 61, 31, 131, 67, 139, 71, 73, 37, 311, 79, 163, 41, 5503, 43, 89, 367, 751, 47, 97, 199, 101, 103, 211, 53, 109, 223, 113, 463, 241663, 59, 487, 61

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..650

Hans Riesel, Some large prime numbers. Translated from the Swedish original (Några stora primtal, Elementa 39 (1956), pp. 258-260) by Lars Blomberg.

MATHEMATICA

getm[n_]:=Module[{m=0}, While[!PrimeQ[n 2^m-1], m++]; n 2^m-1]; Array[getm, 80] (* Harvey P. Dale, Apr 24 2011 *)

PROG

(Haskell)

a038699 = until ((== 1) . a010051) ((+ 1) . (* 2)) . (subtract 1)

-- Reinhard Zumkeller, Mar 05 2012