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%I #17 Mar 22 2024 18:41:39
%S 23,47,233,223,13367,431,2351,6361,179951,193707721,228479,439,2687,
%T 167,11447,7432339208719,2550183799,745988807,3391,263,
%U 32032215596496435569,5625767248687,86656268566282183151,18121,852133201,150287,2349023,730753,359,43441,383
%N Smallest prime factor of composite Mersenne numbers.
%H Max Alekseyev, <a href="/A136030/b136030.txt">Table of n, a(n) for n = 1..188</a>
%t 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
%o (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
%Y Cf. A049479, A016047.
%K nonn
%O 1,1
%A _Artur Jasinski_, Dec 11 2007
%E More terms from _Michel Marcus_, May 14 2014
%E Terms to a(150) in b-file from _Charles R Greathouse IV_, May 14 2014
%E a(151)-a(188) in b-file added at the suggestion of Eric Chen by _Max Alekseyev_, Apr 25 2022