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 A375266 #17 Aug 16 2024 04:27:57 %S A375266 1,2,1,3,1,4,2,1,5,16,8,4,2,1,6,2,1,7,22,11,34,17,52,26,13,40,20,10,5, %T A375266 16,8,4,2,1,8,4,2,1,9,3,1,10,5,16,8,4,2,1,11,34,17,52,26,13,40,20,10, %U A375266 5,16,8,4,2,1,12,4,2,1,13,40,20,10,5,16,8,4,2,1 %N A375266 Irregular triangle read by rows in which row n lists the iterates of the A375265 map from n to 1. %C A375266 By definition the trajectory ends when 1 is reached, so row 1 does not contain the cycle 1 -> 4 -> 2 -> 1. %C A375266 See A375265 for links. %H A375266 Paolo Xausa, <a href="/A375266/b375266.txt">Table of n, a(n) for n = 1..12824</a> (rows 1..300 of the triangle, flattened). %H A375266 <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a>. %e A375266 Triangle begins: %e A375266 1; %e A375266 2, 1; %e A375266 3, 1; %e A375266 4, 2, 1; %e A375266 5, 16, 8, 4, 2, 1; %e A375266 6, 2, 1; %e A375266 7, 22, 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1; %e A375266 8, 4, 2, 1; %e A375266 9, 3, 1; %e A375266 10, 5, 16, 8, 4, 2, 1; %e A375266 ... %t A375266 A375265[n_] := Which[Divisible[n, 3], n/3, Divisible[n, 2], n/2, True, 3*n + 1]; %t A375266 Array[NestWhileList[A375265, #, # > 1 &] &, 15] %Y A375266 Cf. A375265, A375267 (# of iterations), A375268 (row sums), A375280 (row maxs). %Y A375266 Cf. A070165, A070168, A235795, A350279, A350548. %K A375266 nonn,tabf,easy %O A375266 1,2 %A A375266 _Paolo Xausa_, Aug 08 2024