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%I #26 Dec 23 2015 02:58:21
%S 0,0,2,3,2,3,4,4,5,2,3,4,5,6,3,5,6,7,2,4,5,6,7,8,3,4,6,7,8,9,2,3,4,5,
%T 6,7,8,9,10,5,7,8,9,10,11,2,3,4,5,6,7,8,9,10,11,12,3,4,5,6,8,9,10,11,
%U 12,13,2,4,6,7,8,9,10,11,12,13,14,3,5,6,7,9,10,11,12,13,14,15,2,3,4,5,6,7
%N Triangle read by rows in which row n lists the proper nondivisors of n, or zero if n <= 2.
%C Define "proper nondivisors of n" as the positive numbers less than n that do not divide n.
%C Note that a(1) = 0 and a(2) = 0, by convention.
%C Row sums give A024816.
%C Row products give A055067, except the first two rows. - _Reinhard Zumkeller_, Feb 06 2012
%C T(n,1) = A199968(n). - _Reinhard Zumkeller_, Oct 02 2015
%C The n-th row has A049820(n) terms. - _Michel Marcus_, Dec 23 2015
%H Reinhard Zumkeller, <a href="/A173540/b173540.txt">Rows n=1..150 of triangle, flattened</a>
%e If written as a triangle:
%e 0;
%e 0;
%e 2;
%e 3;
%e 2, 3, 4;
%e 4, 5;
%e 2, 3, 4, 5, 6;
%e 3, 5, 6, 7;
%e 2, 4, 5, 6, 7, 8;
%e 3, 4, 6, 7, 8, 9;
%e 2, 3, 4, 5, 6, 7, 8, 9, 10;
%e 5, 7, 8, 9, 10, 11;
%e 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12;
%e 3, 4, 5, 6, 8, 9, 10, 11, 12, 13;
%e 2, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14;
%e 3, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15;
%t Join[{0, 0}, Flatten[Table[Complement[Range[n], Divisors[n]], {n, 1, 20}]]] (* _Geoffrey Critzer_, Dec 13 2014 *)
%o (Haskell)
%o a173540 n k = a173540_row n !! (k-1)
%o a173540_row n = a173540_tabf !! (n-1)
%o a173540_tabf = [0] : [0] : map
%o (\v -> [w | w <- [2 .. v - 1], mod v w > 0]) [3..]
%o -- _Reinhard Zumkeller_, Oct 02 2015, Feb 06 2012
%Y Cf. A027750, A049820, A177235.
%Y Cf. A199968, A024816 (row sums).
%K easy,nonn,tabf
%O 1,3
%A _Omar E. Pol_, May 24 2010
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