%I A005110 M4783
%S A005110 11,29,31,41,43,53,61,71,79,101,103,113,127,131,137,149,151,157,181,191,
%T A005110 197,211,223,229,239,241,251,271,281,293,307,313,337,379,389,401,409,
%U A005110 421,439,443,449,457,491,521,541,547,571,593,601,613,631,641,647,653,673
%N A005110 Class 2- primes.
%D A005110 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A005110 R. K. Guy, Unsolved Problems in Number Theory, A18.
%H A005110 R. J. Mathar, <a href="b005110.txt">Table of n, a(n) for n = 1..13766</
               a>
%t A005110 PrimeFactors[n_Integer] := Flatten[ Table[ #[[1]], {1}] & /@ FactorInteger[n]];
%t A005110 f[n_Integer] := Block[{m = n}, If[m == 0, m = 1, While[ IntegerQ[m/2], 
               m /= 2];
%t A005110 While[ IntegerQ[m/3], m /= 3]];
%t A005110 Apply[Times, PrimeFactors[m] - 1]];
%t A005110 ClassMinusNbr[n_] := Length[NestWhileList[f, n, UnsameQ, All]] - 3;
%t A005110 Prime[ Select[ Range[122], ClassMinusNbr[ Prime[ # ]] == 2 &] ] (* Robert 
               G. Wilson v*)
%Y A005110 Cf. A005113, A056637, A005109, A005111, A005112, A081424, A081425, A081426, 
               A081427, A081428, A081429, A081430.
%Y A005110 Sequence in context: A061086 A034276 A072711 this_sequence A059337 A126240 
               A124110
%Y A005110 Adjacent sequences: A005107 A005108 A005109 this_sequence A005111 A005112 
               A005113
%K A005110 nonn
%O A005110 1,1
%A A005110 N. J. A. Sloane (njas(AT)research.att.com), Simon Plouffe (simon.plouffe(AT)gmail.com)
%E A005110 Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Mar 20 
               2003
%E A005110 Corrected by R. J. Mathar, Feb 01 2007