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A033480 3x + 1 sequence beginning at 15. 0
15, 46, 23, 70, 35, 106, 53, 160, 80, 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, 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, 4, 2, 1, 4, 2, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Table of n, a(n) for n=0..92.

Index entries for sequences related to 3x+1 (or Collatz) problem

Index entries for linear recurrences with constant coefficients, signature (0,0,1).

FORMULA

a(0) = 15, a(n) = a(n - 1)/2 if a(n - 1) is even or 3a(n - 1) + 1 if a(n - 1) is odd.

EXAMPLE

15 is odd, so the next term is 3 * 15 + 1 = 46.

46 is even, so the next term is 46/2 = 23.

MATHEMATICA

NestList[If[EvenQ[#], #/2, 3# + 1] &, 15, 100] (* Harvey P. Dale, Dec 27 2011 *)

PROG

(PARI) a(n)=my(k=15); for(i=1, n, k=if(k%2, k/2, 3*k+1)); k \\ Charles R Greathouse IV, May 04 2015

CROSSREFS

Cf. A033479.

Sequence in context: A068513 A267079 A290583 * A041434 A136430 A139278

Adjacent sequences:  A033477 A033478 A033479 * A033481 A033482 A033483

KEYWORD

nonn,easy

AUTHOR

Jeff Burch

STATUS

approved

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Last modified June 16 14:56 EDT 2019. Contains 324152 sequences. (Running on oeis4.)