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A173540
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Triangle read by rows in which row n lists the proper nondivisors of n, or zero if n <= 2.
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13
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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, 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, 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
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OFFSET
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1,3
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COMMENTS
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Define "proper nondivisors of n" as the positive numbers less than n that do not divide n.
Note that a(1) = 0 and a(2) = 0, by convention.
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LINKS
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EXAMPLE
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If written as a triangle:
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, 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, 12, 13;
2, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14;
3, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15;
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MATHEMATICA
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Join[{0, 0}, Flatten[Table[Complement[Range[n], Divisors[n]], {n, 1, 20}]]] (* Geoffrey Critzer, Dec 13 2014 *)
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PROG
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(Haskell)
a173540 n k = a173540_row n !! (k-1)
a173540_row n = a173540_tabf !! (n-1)
a173540_tabf = [0] : [0] : map
(\v -> [w | w <- [2 .. v - 1], mod v w > 0]) [3..]
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CROSSREFS
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KEYWORD
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easy,nonn,tabf
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AUTHOR
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STATUS
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approved
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