OFFSET
1,3
COMMENTS
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.
Row sums give A024816.
Row products give A055067, except the first two rows. - Reinhard Zumkeller, Feb 06 2012
T(n,1) = A199968(n). - Reinhard Zumkeller, Oct 02 2015
The n-th row has A049820(n) terms. - Michel Marcus, Dec 23 2015
LINKS
Reinhard Zumkeller, Rows n=1..150 of triangle, flattened
EXAMPLE
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;
MATHEMATICA
Join[{0, 0}, Flatten[Table[Complement[Range[n], Divisors[n]], {n, 1, 20}]]] (* Geoffrey Critzer, Dec 13 2014 *)
PROG
(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..]
-- Reinhard Zumkeller, Oct 02 2015, Feb 06 2012
CROSSREFS
KEYWORD
easy,nonn,tabf
AUTHOR
Omar E. Pol, May 24 2010
STATUS
approved