A136030 Smallest prime factor of composite Mersenne numbers.

23, 47, 233, 223, 13367, 431, 2351, 6361, 179951, 193707721, 228479, 439, 2687, 167, 11447, 7432339208719, 2550183799, 745988807, 3391, 263, 32032215596496435569, 5625767248687, 86656268566282183151, 18121, 852133201, 150287, 2349023, 730753, 359, 43441, 383

Offset: 1

Author

Artur Jasinski, Dec 11 2007

Keywords

• nonn

Links

• Max Alekseyev, Table of n, a(n) for n = 1..188

Crossrefs

Cf. A049479, A016047.

Programs

Mathematica

a = {}; Do[If[PrimeQ[n] && !PrimeQ[2^n - 1], w = 2^n - 1; c = FactorInteger[w]; b = c[[1]][[1]]; AppendTo[a, b]], {n, 2, 130}]; a

PARI

lista() = {vi = readvec("c:/gp/bfiles/b054723.txt"); vm = vector(#vi, i, 2^vi[i]-1); for (i=1, #vm, print1(factor(vm[i])[1, 1], ", "););} \\ Michel Marcus, May 14 2014

Extensions

More terms from Michel Marcus, May 14 2014

Terms to a(150) in b-file from Charles R Greathouse IV, May 14 2014

a(151)-a(188) in b-file added at the suggestion of Eric Chen by Max Alekseyev, Apr 25 2022