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

0,4

Links

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

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

Crossrefs

Cf. A222752, A222753, A222755.

Sequence in context: A268904 A058896 A186748 * A181905 A350826 A008403

Adjacent sequences: A222751 A222752 A222753 * A222755 A222756 A222757

Keyword

nonn

Author

T. D. Noe, Mar 04 2013

Status

approved