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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. 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 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: A244314 A014489 A286270 * A167455 A159752 A228089 Adjacent sequences:  A033956 A033957 A033958 * A033960 A033961 A033962 KEYWORD nonn,nice AUTHOR 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 Offset corrected by Reinhard Zumkeller, Jan 08 2014 STATUS approved

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Last modified September 22 03:15 EDT 2018. Contains 315267 sequences. (Running on oeis4.)