A008878 3x+1 sequence starting at 39.

39, 118, 59, 178, 89, 268, 134, 67, 202, 101, 304, 152, 76, 38, 19, 58, 29, 88, 44, 22, 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn

References

• R. K. Guy, Unsolved Problems in Number Theory, E16.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..200
• Index entries for sequences related to 3x+1 (or Collatz) problem
• Index entries for linear recurrences with constant coefficients, signature (0,0,1).

Crossrefs

Row 39 of A347270.

Programs

Magma

[n eq 1 select 39 else IsOdd(Self(n-1)) select 3*Self(n-1)+1 else Self(n-1) div 2: n in [1..70]]; // Vincenzo Librandi, Jul 29 2014

Maple

f := proc(n) option remember; if n = 0 then 39; elif f(n-1) mod 2 = 0 then f(n-1)/2 else 3*f(n-1)+1; fi; end;

Mathematica

NestList[If[EvenQ[#], #/2, 3# + 1]&, 39, 100] (* Vincenzo Librandi, Jul 29 2014 *)