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 A005110 Class 2- primes (for definition see A005109). (Formerly M4783) 15
 11, 29, 31, 41, 43, 53, 61, 71, 79, 101, 103, 113, 127, 131, 137, 149, 151, 157, 181, 191, 197, 211, 223, 229, 239, 241, 251, 271, 281, 293, 307, 313, 337, 379, 389, 401, 409, 421, 439, 443, 449, 457, 491, 521, 541, 547, 571, 593, 601, 613, 631, 641, 647, 653, 673 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES R. K. Guy, Unsolved Problems in Number Theory, A18. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS R. J. Mathar, Table of n, a(n) for n = 1..13766 MATHEMATICA PrimeFactors[n_Integer] := Flatten[ Table[ #[[1]], {1}] & /@ FactorInteger[n]]; f[n_Integer] := Block[{m = n}, If[m == 0, m = 1, While[ IntegerQ[m/2], m /= 2]; While[ IntegerQ[m/3], m /= 3]]; Apply[Times, PrimeFactors[m] - 1]]; ClassMinusNbr[n_] := Length[NestWhileList[f, n, UnsameQ, All]] - 3; Prime[ Select[ Range[122], ClassMinusNbr[ Prime[ # ]] == 2 &] ] (* Robert G. Wilson v *) CROSSREFS Cf. A005113, A056637, A005109, A005111, A005112, A081424, A081425, A081426, A081427, A081428, A081429, A081430. Sequence in context: A196357 A196360 A072711 * A059337 A126240 A124110 Adjacent sequences:  A005107 A005108 A005109 * A005111 A005112 A005113 KEYWORD nonn AUTHOR EXTENSIONS Edited and extended by Robert G. Wilson v, Mar 20 2003 Corrected by R. J. Mathar, Feb 01 2007 STATUS approved

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Last modified May 23 07:08 EDT 2019. Contains 323508 sequences. (Running on oeis4.)