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 A176867 #3 Mar 30 2012 17:22:56 %S A176867 1,0,0,0,0,5,0,3,0,13,0,53,17,35,11,23,7,15,29,9,19,37,77,25,49,99,33, %T A176867 65,131,43,87,173,57,115,39,79,153,305,105,203,407,135,271,541,185, %U A176867 361,123,247,481,169,329,641,219,427,159,295,569,1139,379,759,283,505,1011 %N A176867 Least odd number that requires n Collatz (3x+1) iterations to reach 1, or zero if there is no such number. %C A176867 Both the 3x+1 steps and the halving steps are counted. a(n)=0 only for n = 1, 2, 3, 4, 6, 8, and 10. Sequence A033491 gives the least even or odd number requiring n iterations. %H A176867 T. D. Noe, <a href="/A176867/b176867.txt">Table of n, a(n) for n=0..1924</a> %Y A176867 Cf. A176866, A176868 %K A176867 nonn %O A176867 0,6 %A A176867 _T. D. Noe_, Apr 27 2010