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 A275531 #7 Feb 16 2025 08:33:36 %S A275531 1,3,7,15,31,36,46,49,55,63,66,67,91,106,119,127,139,145,148,186,190, %T A275531 197,214,235,248,255,259,274,281,288,301,302,316,325,330,339,346,357, %U A275531 386,393,399,413,427,442,442,452,465,497,498,500,505,509,511,519,535,540 %N A275531 Values taken by the sum of numbers in Collatz trajectory (A033493), sorted into ascending order. %C A275531 Values a(n) such that a(n) = a(n+1): 442, 609, 633, 724, 904, 925, ... %H A275531 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CollatzProblem.html">Collatz Problem</a> %H A275531 Wikipedia, <a href="http://en.wikipedia.org/wiki/Collatz_conjecture">Collatz conjecture</a> %o A275531 (Magma) Sort([&+[k eq 1 select n else IsOdd(Self(k-1)) and not IsOne(Self(k-1)) select 3*Self(k-1)+1 else Self(k-1) div 2: k in [1..5*n]]: n in [1..2^10] | &+[k eq 1 select n else IsOdd(Self(k-1)) and not IsOne(Self(k-1)) select 3*Self(k-1)+1 else Self(k-1) div 2: k in [1..5*n]] le 2^10]) %Y A275531 Cf. A033493, A275532. %K A275531 nonn %O A275531 1,2 %A A275531 _Jaroslav Krizek_, Jul 31 2016