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 A062058 #26 Feb 16 2025 08:32:44 %S A062058 25,49,50,51,98,99,100,101,102,196,197,198,200,202,204,205,217,392, %T A062058 394,396,397,400,404,405,408,410,433,434,435,441,475,784,788,789,792, %U A062058 794,800,808,810,816,820,821,833,857,866,867,868,869,870,875,882,883,950,951,953 %N A062058 Numbers with 8 odd integers in their Collatz (or 3x+1) trajectory. %C A062058 The Collatz (or 3x+1) function is f(x) = x/2 if x is even, 3x+1 if x is odd. %C A062058 The Collatz trajectory of n is obtained by applying f repeatedly to n until 1 is reached. %C A062058 A078719(a(n)) = 8; A006667(a(n)) = 7. %D A062058 J. Shallit and D. Wilson, The "3x+1" Problem and Finite Automata, Bulletin of the EATCS #46 (1992) pp. 182-185. %H A062058 Reinhard Zumkeller, <a href="/A062058/b062058.txt">Table of n, a(n) for n = 1..1000</a> %H A062058 J. Shallit and D. Wilson, <a href="http://www.cs.uwaterloo.ca/~shallit/Papers/wilson.ps">The "3x+1" Problem and Finite Automata</a>, Bulletin of the EATCS #46 (1992) pp. 182-185. %H A062058 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CollatzProblem.html">Collatz Problem</a> %H A062058 Wikipedia, <a href="http://en.wikipedia.org/wiki/Collatz_conjecture">Collatz conjecture</a> %H A062058 <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a> %H A062058 <a href="/index/Ar#2-automatic">Index entries for 2-automatic sequences</a>. %e A062058 The Collatz trajectory of 25 is (25, 76, 38, 19, 58, 29, 88, 44, 22, 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1), which contains 8 odd integers. %t A062058 Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; countOdd[lst_] := Length[Select[lst, OddQ]]; Select[Range[1000], countOdd[Collatz[#]] == 8 &] (* _T. D. Noe_, Dec 03 2012 *) %o A062058 (Haskell) %o A062058 import Data.List (elemIndices) %o A062058 a062058 n = a062058_list !! (n-1) %o A062058 a062058_list = map (+ 1) $ elemIndices 8 a078719_list %o A062058 -- _Reinhard Zumkeller_, Oct 08 2011 %Y A062058 Cf. A062052-A062060. %Y A062058 Column k=8 of A354236. %K A062058 nonn %O A062058 1,1 %A A062058 _David W. Wilson_