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A241837 Irregular triangular array of denominators of the positive rational numbers ordered as in Comments.

%I A241837 #4 Jun 19 2014 11:15:34
%S A241837 1,1,1,1,1,1,1,1,7,5,1,1,1,1,1,4,11,5,3,2,7,5,1,1,1,1,5,5,7,13,8,10,4,
%T A241837 11,5,3,2,7,5,1,1,1,1,2,19,3,17,13,17,11,4,13,14,19,5,5,7,13,8,10,4,
%U A241837 11,5,3,2,7,5,1,1,1,1,7,23,11,7,6,8,19,7,23
%N A241837 Irregular triangular array of denominators of the positive rational numbers ordered as in Comments.
%C A241837 Decree that (row 1) = (1,2,3).  For n >=2, row n consists of numbers in increasing order generated as follows:  x+4 for each x in row n-1 together with 12/x for each nonzero x in row n-1, where duplicates are deleted as they occur.  Every rational number occurs exactly once in the array.  The number of numbers in row n is A022095(n-1) for n >= 4.
%H A241837 Clark Kimberling, <a href="/A241837/b241837.txt">Table of n, a(n) for n = 1..5000</a>
%e A241837 First 4 rows of the array of rationals:
%e A241837 1/1 .. 2/1 ... 3/1
%e A241837 4/1 .. 5/1 ... 6/2 . 7/1 . 12/1
%e A241837 12/7 . 12/5 .. 8/1 . 9/1 . 10/1 . 11/1 . 16/1
%e A241837 3/4 .. 12/11 . 6/5 . 4/3 . 3/2 .. 40/7 . 32/5 . 13/1 . 14/1 . 15/1 . 20/1
%e A241837 The denominators, by rows:  1,1,1,1,1,2,1,1,7,5,1,1,1,1,1,4,11,5,3,2,7,5,1,1,1,1.
%t A241837 z = 10; g[1] = {1, 2, 3}; f1[x_] := x + 4; f2[x_] := 12/x;  h[1] = g[1];
%t A241837 b[n_] := b[n] = DeleteDuplicates[Union[f1[g[n - 1]], f2[g[n - 1]]]];
%t A241837 h[n_] := h[n] = Union[h[n - 1], g[n - 1]];
%t A241837 g[n_] := g[n] = Complement [b[n], Intersection[b[n], h[n]]]
%t A241837 u = Table[g[n], {n, 1, z}]
%t A241837 v = Flatten[u]
%t A241837 Denominator[v]  (* A241837 *)
%t A241837 Numerator[v]    (* A243575 *)
%Y A241837 Cf. A243575, A243924, A022095.
%K A241837 nonn,easy,tabf,frac
%O A241837 1,9
%A A241837 _Clark Kimberling_, Jun 15 2014