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 A355568 #18 Oct 14 2022 08:54:59
%S A355568 8,10,16,20,26,34,40,52,92,122,160,167,184,244,251,334,377,412,433,
%T A355568 488,502,650,668,866,890,976,1154,1186,1300,1336,1732,1780,2308,3644,
%U A355568 4858,7288
%N A355568 Numbers k > 4 in a Collatz trajectory reaching k after starting at k-1.
%H A355568 <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a>
%F A355568 a(n) = A070993(n+1) + 1.
%e A355568 8 is a term because the orbit started at 8 - 1 = 7 reaches 8:
%e A355568 7 -> 22 -> 11 -> 34 -> 17 -> 52 -> 26 -> 13 -> 40 -> 20 -> 10 -> 5 -> 16 -> 8;
%e A355568 10 is a term because it is in the orbit starting at 10 - 1 = 9:
%e A355568 9 -> 28 -> 14 -> 7 -> 22 -> 11 -> 34 -> 17 -> 52 -> 26 -> 13 -> 40 -> 20 -> 10.
%o A355568 (PARI) collatz(start,target) = {my(old=start,new=0); while (new!=target && new!=1, if(old%2==0, new=old/2, new=3*old+1); old=new); new>1};
%o A355568 for (k=5, 10000, if(collatz(k-1,k), print1(k,", ")))
%Y A355568 Cf. A006370, A006577, A070991, A070993, A355239, A355240, A355569.
%K A355568 nonn,more
%O A355568 1,1
%A A355568 _Hugo Pfoertner_, Jul 10 2022