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A222755 Greatest odd number k such that difference between halving and tripling steps in Collatz (3x+1) trajectory of k is n, or 0 if there is no such k. 3

%I #9 Mar 05 2013 14:57:34

%S 1,0,0,5,0,21,17,85,113,341,453,1365,1813,5461,7281,21845,29125,87381,

%T 116501,349525,466033,1398101,1864133,5592405,7456533,22369621,

%U 29826161,89478485,119304645,357913941,477218581,1431655765

%N Greatest odd number k such that difference between halving and tripling steps in Collatz (3x+1) trajectory of k is n, or 0 if there is no such k.

%C Note that a(n) <= 2^n, with equality only for n = 0.

%t Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; nn = 15; t = Table[0, {nn}]; Do[c = Collatz[n]; e = Select[c, EvenQ]; diff = 2*Length[e] - Length[c]; If[diff < nn - 1, t[[diff + 2]] = n], {n, 1, 2^(nn - 1), 2}]; t

%Y Cf. A222752, A222753, A222754.

%K nonn

%O 0,4

%A _T. D. Noe_, Mar 04 2013

%E a(31) added - _T. D. Noe_, Mar 05 2013

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Last modified March 28 13:35 EDT 2024. Contains 371254 sequences. (Running on oeis4.)