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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(n-6) - a(n-12) 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

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Last modified May 27 06:24 EDT 2019. Contains 323599 sequences. (Running on oeis4.)