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A033959
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Record number of steps to reach 1 in `3x+1' problem, corresponding to starting values in A033958.
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3
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0, 2, 5, 6, 7, 41, 42, 43, 44, 45, 46, 47, 52, 62, 65, 66, 76, 79, 87, 96, 98, 101, 102, 103, 113, 114, 119, 125, 129, 130, 138, 141, 142, 164, 166, 174, 189, 195, 196, 197, 207, 208, 209, 217, 222, 228, 248, 256, 257, 258, 263, 278, 357, 358, 359, 362, 370
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Only the 3x+1 steps not the halving steps are counted.
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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.
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LINKS
| Index entries for sequences from "Goedel, Escher, Bach"
Index entries for sequences related to 3x+1 (or Collatz) problem
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MAPLE
| A033959 := 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;
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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 ] ] ] ]
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CROSSREFS
| Cf. A006884, A006885, A006877, A006878, A033492, A033958.
Sequence in context: A117548 A175135 A014489 * A167455 A159752 A126971
Adjacent sequences: A033956 A033957 A033958 * A033960 A033961 A033962
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KEYWORD
| nonn,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Winston C. Yang (winston(AT)cs.wisc.edu), Aug 27 2000 and from Larry Reeves (larryr(AT)acm.org), Sep 27 2000
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