

A133419


Image of n under one application of the "5x+1" map.


9



6, 1, 1, 2, 26, 3, 36, 4, 3, 5, 56, 6, 66, 7, 5, 8, 86, 9, 96, 10, 7, 11, 116, 12, 126, 13, 9, 14, 146, 15, 156, 16, 11, 17, 176, 18, 186, 19, 13, 20, 206, 21, 216, 22, 15, 23, 236, 24, 246, 25, 17, 26, 266, 27, 276, 28, 19, 29, 296, 30, 306, 31, 21, 32, 326, 33, 336, 34, 23, 35
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

The 5x+1 map sends x to x/2 if x is even, x/3 if x is odd and divisible by 3, otherwise 5x+1.


LINKS

Table of n, a(n) for n=1..70.
Tomás Oliveira e Silva, The px+1 problem
Index entries for sequences related to 3x+1 (or Collatz) problem


FORMULA

From Chai Wah Wu, Mar 04 2018: (Start)
a(n) = 2*a(n6)  a(n12) for n > 12.
G.f.: x*(4*x^10 + x^9 + x^8 + 2*x^7 + 24*x^6 + 3*x^5 + 26*x^4 + 2*x^3 + x^2 + x + 6)/(x^12  2*x^6 + 1). (End)


MATHEMATICA

Table[If[EvenQ[n], n/2, If[Mod[n, 3] == 0, n/3, 5*n + 1]], {n, 1, 80}] (* Stefan Steinerberger, Feb 16 2008 *)
Table[Which[EvenQ[n], n/2, Divisible[n, 3], n/3, True, 5n+1], {n, 70}] (* Harvey P. Dale, Jul 08 2018 *)


PROG

(PARI) a(n)=if(n%2, if(n%3, 5*n+1, n/3), n/2) \\ Charles R Greathouse IV, Sep 02 2015


CROSSREFS

Cf. A133420.
Sequence in context: A073354 A197420 A128423 * A010134 A019713 A155824
Adjacent sequences: A133416 A133417 A133418 * A133420 A133421 A133422


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane, Nov 27 2007


EXTENSIONS

More terms from Stefan Steinerberger, Feb 16 2008
Comment clarified by Chai Wah Wu, Mar 04 2018


STATUS

approved



