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%I #12 Jul 23 2022 23:07:48
%S 5,13,17,21,45,53,69,85,113,141,181,213,241,277,301,321,341,369,401,
%T 453,565,725,753,853,909,965,1069,1109,1137,1205,1285,1365,1425,1477,
%U 1605,1713,1813,1933,1969,2261,2417,2573,2577,2625,2901,2957,3013,3213,3413
%N Odd numbers n such that the reduced Collatz map n -> (3n+1)/2^k gives a trajectory of decreasing odd numbers.
%H <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a>
%e 45 is in the sequence because 45 generates the trajectory of odd numbers : 45 -> 17 -> -> 13 -> 5 -> 1.
%p for n from 3 by 2 to 5000 do:i:=0:x:=n:n0:=n: u0:=0:for it from 1 to 1000 while(n0<>1 and u0=0) do: for a from 1 to 100 while(x mod 2 = 0 ) do: i:=i+1:x:=x/2: od:if x > n0 then u0:=1:else i:=i+1:n0:=x :x:=3*n0+1: fi:od: if u0=0 then printf(`%d, `,n):else fi:od:
%Y Cf. A006666, A075677 (reduced Collatz map), A256598 (trajectory).
%K nonn
%O 1,1
%A _Michel Lagneau_, Apr 10 2012
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