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A033958 In the `3x+1' problem, these values for the starting value set new records for number of steps to reach 1. 5
1, 3, 7, 9, 25, 27, 73, 97, 129, 171, 231, 313, 327, 703, 871, 1161, 2463, 2919, 3711, 6171, 10971, 13255, 17647, 23529, 26623, 34239, 35655, 52527, 77031, 106239, 142587, 156159, 216367, 230631, 410011, 511935, 626331, 837799, 1117065, 1501353, 1723519, 2298025, 3064033 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Only the 3x+1 steps, not the halving steps, are counted.

REFERENCES

D. R. Hofstadter, Goedel, Escher, Bach: an Eternal Golden Braid, Random House, 1980, p. 400.

B. Hayes, Computer Recreations: On the ups and downs of hailstone numbers, Scientific American, 250 (No. 1, 1984), pp. 10-16.

G. T. Leavens and M. Vermeulen, 3x+1 search problems, Computers and Mathematics with Applications, 24 (1992), 79-99.

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..71

Index entries for sequences from "Goedel, Escher, Bach"

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

MAPLE

A033958 := proc(n) local a, L; L := 0; a := n; while a <> 1 do if a mod 2 = 0 then a := a/2; else a := 3*a+1; L := L+1; fi; od: RETURN(L); end;

MATHEMATICA

f[ nn_ ] := Module[ {c, n}, c = 0; n = nn; While[ n != 1, If[ Mod[ n, 2 ] == 0, n /= 2, n = 3*n + 1; c++ ] ]; Return[ c ] ] maxx = -1; For[ n = 1, n <= 10^8, n++, Module[ {val}, val = f[ n ]; If[ val > maxx, maxx = val; Print[ n, " ", val ] ] ] ]

PROG

(Haskell)

a033958 n = a033958_list !! (n-1)

-- For definition of a033958_list: see A033959.

-- Reinhard Zumkeller, Jan 08 2014

CROSSREFS

Cf. A006884, A006885, A006877, A006878, A033492, A033959.

Sequence in context: A099886 A118564 A098338 * A018827 A249664 A057840

Adjacent sequences:  A033955 A033956 A033957 * A033959 A033960 A033961

KEYWORD

nonn,nice

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Jud McCranie, Jan 26 2000.

Corrected with Mathematica code by Winston C. Yang (winston(AT)cs.wisc.edu), Aug 27 2000

a(40)-a(43) from Charles R Greathouse IV, Oct 07 2013

STATUS

approved

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Last modified September 25 21:33 EDT 2017. Contains 292500 sequences.