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 A221467 #4 Jan 17 2013 13:38:40 %S A221467 1,2,4,8,16,32,33,64,66,128,129,132,133,256,258,264,266,512,513,516, %T A221467 528,529,532,1024,1026,1032,1056,1058,1064,2048,2049,2052,2064,2112, %U A221467 2113,2116,2128,4096,4098,4104,4105,4128,4224,4226,4232,4233,4256,8192,8193 %N A221467 The Collatz (3x+1) iteration in A220145 sorted and converted to decimal. %C A221467 Sequence A005186 tells how many of these numbers are in [2^n, 2^(n+1)-1]. %K A221467 nonn,base %O A221467 1,2 %A A221467 _T. D. Noe_, Jan 17 2013