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A056959 In repeated iterations of function m->m/2 if m even, m->3m+1 if m odd, a(n) is maximum value achieved if starting from n. 3
4, 4, 16, 4, 16, 16, 52, 8, 52, 16, 52, 16, 40, 52, 160, 16, 52, 52, 88, 20, 64, 52, 160, 24, 88, 40, 9232, 52, 88, 160, 9232, 32, 100, 52, 160, 52, 112, 88, 304, 40, 9232, 64, 196, 52, 136, 160, 9232, 48, 148, 88, 232, 52, 160, 9232, 9232, 56, 196, 88, 304, 160, 184 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

If a(n) exists (which is the essence of the 3x+1 "problem") then a(n) must be a multiple of 4, since if a(n) was odd then the next iteration 3*a(n)+1 would be greater than a(n), while if a(n) was twice an odd number then the next-but-one iteration (3/2)*a(n)+1 would be greater.

LINKS

Table of n, a(n) for n=1..61.

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

EXAMPLE

a(6)=16 since iteration starts: 6, 3, 10, 5, 16, 8, 4, 2, 1, 4, 2, 1, ... and 16 is highest value

PROG

(PARI) a(n)=my(r=max(4, n)); while(n>2, if(n%2, n=3*n+1; if(n>r, r=n), n/=2)); r \\ Charles R Greathouse IV, Jul 19 2011

CROSSREFS

Cf. A006370, A056957, A056958.

Essentially the same as A025586.

Sequence in context: A177241 A076821 A165825 * A255300 A255298 A255302

Adjacent sequences:  A056956 A056957 A056958 * A056960 A056961 A056962

KEYWORD

nonn

AUTHOR

Henry Bottomley, Jul 18 2000

STATUS

approved

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Last modified February 16 21:59 EST 2019. Contains 320200 sequences. (Running on oeis4.)