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%I #7 May 26 2018 12:29:41
%S 15,21,55,33,39,85,51,57,115,69,203,145,87,93,259,185,111,205,123,129,
%T 235,141,371,265,159,413,295,177,183,469,335,201,355,213,219,553,395,
%U 237,415,249,623,445,267,1313,679,485,291,505,303,309,535,321,327,565
%N Least number having exactly two odd prime factors that differ by 2n.
%C The lesser of the two factors is in A002373.
%e We have a(4) = 33 because 33 = 3*11, with 11 - 3 = 2*4, the smallest number with this property. Others are 85 = 5*13, 209 = 11*19, 713 = 23*31, 1073 = 29*37, 3233 = 53*61, ...
%t f[n_] := Block[{p = 3}, While[ ! PrimeQ[p] || ! PrimeQ[p + 2n], p++ ]; p(p + 2n)]; Table[ f[n], {n, 1, 55}]
%t Table[#(#+2n)&/@Select[Prime[Range[2,100]],PrimeQ[#+2n]&,1],{n,60}]// Flatten (* _Harvey P. Dale_, May 26 2018 *)
%Y Cf. A046388.
%K nonn
%O 1,1
%A _Lekraj Beedassy_, Jun 05 2003
%E Edited and extended by _Robert G. Wilson v_, Jun 07 2003