A038699 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

Offset

1,1

Links

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

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

Crossrefs

Primes arising in A040081 (or 0 if no prime exists).

Cf. A040081, A050921.

Cf. A010051, A000079.

Sequence in context: A374902 A122775 A086632 * A249803 A350833 A064655

Adjacent sequences: A038696 A038697 A038698 * A038700 A038701 A038702

Keyword

nonn,easy,nice

Author

N. J. A. Sloane, Dec 30 1999

Extensions

More terms from Henry Bottomley, Apr 24 2001

Status

approved