Numbers n such that n is in the 3x+1 (Colatz) trajectory of n+1.
1, 2, 4, 5, 8, 10, 13, 16, 17, 38, 40, 46, 53, 56, 58, 61, 70, 80, 88, 106, 107, 160, 251, 283, 377, 638, 650, 958, 976, 1367, 1438, 1822, 2158, 2429, 2734, 3238, 4102, 4616, 4858, 6154, 7288, 9232
1
There are no additional terms less than 10^9. Is this a finite sequence?
T. D. Noe, Plot of 42 terms
(Mma) Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; Select[Range[10000], MemberQ[Collatz[# + 1], #] &]
Cf. A070993, A276200 (prime terms), S000964, S000965.
nonn,more
T. D. Noe, Jan 27 2017