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 A033959 Record number of steps to reach 1 in '3x+1' problem, corresponding to starting values in A033958. 4
 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; 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. G. T. Leavens and M. Vermeulen, 3x+1 search problems, Computers and Mathematics with Applications, 24 (1992), 79-99. LINKS Table of n, a(n) for n=1..57. Brian Hayes, Computer Recreations: On the ups and downs of hailstone numbers, Scientific American, 250 (No. 1, 1984), pp. 10-16. Index entries for sequences from "Goedel, Escher, Bach" Index entries for sequences related to 3x+1 (or Collatz) problem 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; 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) a033959 n = a033959_list !! (n-1) (a033959_list, a033958_list) = unzip \$ (0, 1) : f 1 1 where f i x | y > x = (y, 2 * i - 1) : f (i + 1) y | otherwise = f (i + 1) x where y = a075680 i -- Reinhard Zumkeller, Jan 08 2014 CROSSREFS Cf. A006884, A006885, A006877, A006878, A033492, A033958. Cf. A075680. Sequence in context: A346880 A344865 A350130 * A167455 A159752 A352325 Adjacent sequences: A033956 A033957 A033958 * A033960 A033961 A033962 KEYWORD nonn,nice AUTHOR N. J. A. Sloane EXTENSIONS More terms from Winston C. Yang (winston(AT)cs.wisc.edu), Aug 27 2000 More terms from Larry Reeves (larryr(AT)acm.org), Sep 27 2000 Offset corrected by Reinhard Zumkeller, Jan 08 2014 STATUS approved

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Last modified December 10 18:13 EST 2023. Contains 367717 sequences. (Running on oeis4.)