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 A161022 #16 Jul 25 2023 15:42:40 %S A161022 10087,30262,15131,45394,22697,68092,34046,17023,51070,25535,76606, %T A161022 38303,114910,57455,172366,86183,258550,129275,387826,193913,581740, %U A161022 290870,145435,436306,218153,654460,327230,163615,490846,245423,736270 %N A161022 Collatz (or 3x+1) trajectory starting at 10087. %C A161022 10087 = A060412(6); a(A006577(10087)) = a(223) = 1; %C A161022 a(n)=A161021(n-53)=A161023(n+100) for n with 208<=n<=228. %C A161022 At step 221 becomes periodic: 4 2 1 4 2 1 4 2 1 ... - _N. J. A. Sloane_, Jul 27 2019 %H A161022 R. Zumkeller, <a href="/A161022/b161022.txt">Table of n, a(n) for n = 0..223</a> %H A161022 <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a> %H A161022 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,1). %t A161022 NestList[If[EvenQ[#],#/2,3#+1]&,10087,30] (* _Harvey P. Dale_, Jul 25 2023 *) %Y A161022 A008884. %K A161022 nonn,easy %O A161022 0,1 %A A161022 _Reinhard Zumkeller_, Jun 03 2009 %E A161022 Edited by _N. J. A. Sloane_, Jul 27 2019