A008877 3x+1 sequence starting at 57.

57, 172, 86, 43, 130, 65, 196, 98, 49, 148, 74, 37, 112, 56, 28, 14, 7, 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, 2, 1, 4, 2, 1

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

Cf. A006370.

Row 57 of A347270.

Programs

Haskell

a008877 n = a008877_list !! n
a008877_list = 57 : iterate a006370 57
-- Reinhard Zumkeller, Aug 30 2012

Magma

[n eq 1 select 57 else IsOdd(Self(n-1)) select 3*Self(n-1)+1 else Self(n-1) div 2: n in [1..80]]; // Vincenzo Librandi, Jul 29 2014

Maple

f := proc(n) option remember; if n = 0 then 57; 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]&, 57, 100] (* Vincenzo Librandi, Jul 29 2014 *)