A222754 Least 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.

1, 0, 0, 3, 0, 13, 7, 9, 19, 25, 33, 43, 39, 79, 105, 135, 123, 169, 159, 295, 283, 111, 223, 297, 175, 103, 91, 121, 31, 27, 55, 73, 97, 129, 171, 231, 313, 411, 543, 327, 649, 859, 763, 1017, 1351, 1215, 703, 937, 871, 1161, 2223, 3097, 2631, 3567, 3175, 4233

Offset: 0

Author

T. D. Noe, Mar 04 2013

Keywords

• nonn

Links

• T. D. Noe, Table of n, a(n) for n = 0..100

Crossrefs

Cf. A222752, A222753, A222755.

Programs

Mathematica

Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; nn = 51; t = Table[0, {nn}]; n = -1; While[Min[Drop[t, 5]] == 0, n = n + 2; c = Collatz[n]; e = Select[c, EvenQ]; diff = 2*Length[e] - Length[c]; If[diff < nn - 1 && t[[diff + 2]] == 0, t[[diff + 2]] = n]]; t