This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A039505 #9 Dec 19 2015 12:57:35
%S A039505 17,21,23,25,31,33,37,41,45,49,55,61,67,73,83,91,99,109,111,117,123,
%T A039505 131,147,153,163,165,175,179,185,195,197,209,213,219,221,225,229,233,
%U A039505 239,243,247,257,261,263,267,277,279,291,293,295,305,311,313,319,321
%N A039505 Odd numbers from A039502.
%t A039505 colln[n_]:= NestWhile[If[EvenQ[#], #/2, 3#-1] &, n, FreeQ[{1, 5, 17}, #] &]; Select[Range[1, 321, 2], colln[#] == 17 &] (* _Jayanta Basu_, Jun 06 2013 *)
%Y A039505 Cf. A037084, A039500-A039504.
%K A039505 nonn,easy
%O A039505 1,1
%A A039505 _Christian G. Bower_, Feb 15 1999