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 A010120 #20 Jun 19 2017 00:13:41 %S A010120 1,2,3,3,3,21,21,75,75,151,151,1365,1365,5461,5461,14563,14563,87381, %T A010120 87381,184111,184111,932067,932067,5592405,5592405,13256071,13256071, %U A010120 26512143,26512143,357913941,357913941,1431655765,1431655765,3817748707 %N A010120 Smallest start for a '3x+1' sequence containing 2^n. %H A010120 <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a> %F A010120 a(n) = A070167(A000079(n)). - _Reinhard Zumkeller_, Jan 02 2013 %o A010120 (Haskell) %o A010120 a010120 = a070167 . a000079 -- _Reinhard Zumkeller_, Jan 02 2013 %Y A010120 Cf. A054646. %K A010120 nonn,nice %O A010120 0,2 %A A010120 Greg Warrington (waringtn(AT)netcom.com) %E A010120 Corrected and extended by _David W. Wilson_, Jun 15 1997