%I #38 Mar 02 2019 02:14:04

%S 5,3,21,13,85,17,11,7,15,9,19,37,25,49,33,65,43,87,57,39,79,153,105,

%T 203,135,271,185,123,247,169,329,219,159,295,569,379,283,505,377,251,

%U 167,111,223,445,297,593,395,263,175,351,233,155,103,207,137,91,183

%N Least odd number k such that in the Collatz sequence of k there are n even numbers.

%C Previous name was: First number in row n of triangle A199636.

%H Robert G. Wilson v, <a href="/A199637/b199637.txt">Table of n, a(n) for n = 4..573</a> (first 500 terms from T. D. Noe)

%t Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; nn = 100; t = Table[0, {nn}]; cnt = 3; n = 1; While[cnt < nn, n = n + 2; len = Length[Select[Collatz[n], EvenQ]]; If[len <= nn && t[[len]] == 0, t[[len]] = n; cnt++]]; t

%t f = Compile[{{n, _Real}}, Block[{c = 0, k = n}, While[k > 1, c++; If[OddQ@ Round@ k, k = (3k + 1)/2, k /= 2]]; c]]; k = 1; t[_] := 0; While[k < 2101, If[t@ f@ k == 0, t@ f@ k = k;]; k += 2]; t@# & /@ Range@ 100 (* _Robert G. Wilson v_, Mar 06 2018 *)

%Y Cf. A199636.

%K nonn

%O 4,1

%A _T. D. Noe_, Nov 14 2011

%E New name from _Robert G. Wilson v_, Mar 06 2018