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 A253720 a(n) = length of row n in A253676 and A254068, assuming the 3x+1 (or Collatz) conjecture. 2
 1, 2, 5, 3, 4, 2, 6, 5, 7, 5, 18, 5, 6, 3, 8, 4, 7, 4, 19, 6, 5, 2, 7, 4, 20, 6, 8, 19, 3, 5, 16, 18, 21, 7, 15, 4, 20, 5, 9, 8, 17, 18, 10, 8, 8, 5, 10, 18, 21, 6, 3, 7, 9, 3, 5, 19, 11, 8, 14, 8, 6, 4, 10, 17, 22, 7 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA For n>1, k>=1, a(n) = a((8+(3*n-2)*4^k)/12). MATHEMATICA (* Row lengths of A253676 and A254068: *) v[n_] := IntegerExponent[n, 2]; f[x_] := (3*x + 1)/2^v[3*x + 1]; s[x_] := (3 + (3/2)^v[1 + f[x]]*(1 + f[x]))/6; A253676[n_] := NestWhileList[s[4*# - 3] &, n, # > 1 &]; Table[Length[A253676[n]], {n, 1, 66}] CROSSREFS Cf. A253676, A254068. Sequence in context: A073480 A077057 A030660 * A309735 A275726 A146096 Adjacent sequences:  A253717 A253718 A253719 * A253721 A253722 A253723 KEYWORD nonn AUTHOR L. Edson Jeffery, May 02 2015 STATUS approved

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Last modified May 17 09:03 EDT 2021. Contains 343969 sequences. (Running on oeis4.)