login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A258056 3x + 1 sequence starting at 75. 2
75, 226, 113, 340, 170, 85, 256, 128, 64, 32, 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, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

a(n) gives the value obtained after n iterations of the Collatz function starting at 75. - Daniel Forgues, May 19 2015

a(n) = 1 for the first time with n = 14 (14 iterations); at this point, we get the trivial (1, 4, 2) cycle... (A153727). - Daniel Forgues, May 22 2015

LINKS

Table of n, a(n) for n=0..90.

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

FORMULA

a(0) = 75; a(n) = 3*a(n - 1) + 1 if a(n - 1) is odd, a(n) = a(n - 1)/2 otherwise.

EXAMPLE

75 is odd, so it's followed by 3*75 + 1 = 226.

226 is even, so it's followed by 226/2 = 113.

MATHEMATICA

NestList[If[EvenQ[#], #/2, 3# + 1] &, 75, 100]

PROG

(MAGMA) [n eq 1 select 75 else IsOdd(Self(n-1)) select 3*Self(n-1)+1 else Self(n-1) div 2: n in [1..80]]; // Vincenzo Librandi, May 18 2015

(Sage)

def collatz(start):

    a = start

    while(true):

        yield a

        a = 3*a + 1 if is_odd(a) else a/2

A258056 = collatz(75)

[A258056.next() for _ in range(60)] # Peter Luschny, May 22 2015

CROSSREFS

Cf. A033478, A153727.

Sequence in context: A003503 A201916 A098230 * A174685 A158742 A292313

Adjacent sequences:  A258053 A258054 A258055 * A258057 A258058 A258059

KEYWORD

nonn,easy

AUTHOR

Alonso del Arte, May 17 2015

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 15 23:54 EDT 2019. Contains 328038 sequences. (Running on oeis4.)