A221468 - OEIS

%I #11 Aug 20 2017 10:52:06

%S 1,2,133,4,33,266,67733,8,541865,66,16933,532,529,135466,135253,16,

%T 4233,1083730,1083717,132,129,33866,33813,1064,8669737,1058,

%U 2678946987458595510314019806849701,270932,270929,270506,83717093358081109697313118964053,32,69357897

%N The Collatz (3x+1) iteration in A220145 converted to decimal.

%C Sequence A005186 tells how many of these numbers are in [2^n, 2^(n+1)-1].

%C From _Rémy Sigrist_, Aug 19 2017: (Start)

%C a(2^n) = 2^n for any n >= 0.

%C A000120(a(n)) - 1 = A006667(n) for any n > 0.

%C A070939(a(n)) - 1 = A006577(n) for any n > 0.

%C All terms are Fibbinary numbers (A003714).

%C (End)

%H Rémy Sigrist, <a href="/A221468/b221468.txt">Table of n, a(n) for n = 1..10000</a>

%H <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a>

%t Table[FromDigits[#, 2] &@ Boole@ OddQ@ Reverse@ NestWhileList[If[EvenQ@ #, #/2, 3 # + 1] &, n, # > 1 &], {n, 33}] (* _Michael De Vlieger_, Aug 19 2017 *)

%o (PARI) a(n) = my (v=0, p=1); while (n>1, if (n%2, n = 3*n+1; v += p, n = n/2); p *= 2); return (p+v) \\ _Rémy Sigrist_, Aug 19 2017

%Y Cf. A000120, A003714, A005186, A006577, A006667, A070939, A220145.

%K nonn,base,look

%O 1,2

%A _T. D. Noe_, Jan 17 2013