A217744 Numbers whose Collatz trajectory contains equal number of terms of the form 4k+1 and 4k+3.

15, 30, 60, 120, 151, 239, 240, 255, 302, 377, 423, 425, 478, 479, 480, 510, 593, 604, 669, 685, 743, 754, 755, 846, 847, 850, 851, 939, 956, 958, 960, 1020, 1053, 1057, 1186, 1191, 1208, 1297, 1321, 1338, 1341, 1370, 1375, 1473, 1486, 1487, 1508, 1509, 1510

Offset: 1

Author

Jayanta Basu, Mar 23 2013

Keywords

• nonn

Links

• T. D. Noe, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A070165, A192719, A217743.

Programs

Mathematica

Collatz[n_] :=NestWhileList[If[EvenQ[#], #/2, 3*# + 1] &, n, # > 1 &]; t = {}; Do[If[Length[Select[Collatz[n], Mod[#, 4] == 1 &]] -Length[Select[Collatz[n], Mod[#, 4] == 3 &]] == 0, AppendTo[t, n]], {n, 1500}]; t