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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 Tomás Oliveira e Silva, The px+1 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.)