- A282698 contains A003121 (for triangles with strict "less than" interlacing), and 20, 1744
- A003121
Number of ways to arrange the numbers 1,2,...,n(n+1)/2
in a triangle so that the rows interlace;
e.g. one of the 12 triangles counted by a(4) is
6
4 8
2 5 9
1 3 7 10
- Clark Kimberling, Mar 25 2012
The a(4) = 12 ways to fill a triangle with the numbers 0 through 9:
5 6 6 5
3 7 3 7 2 7 2 7
1 4 8 1 4 8 1 4 8 1 4 8
0 2 6 9 0 2 5 9 0 3 5 9 0 3 6 9
5 3 3 4
3 6 2 6 2 7 3 7
1 4 8 1 5 8 1 5 8 1 5 8
0 2 7 9 0 4 7 9 0 4 6 9 0 2 6 9
4 4 5 4
2 6 2 7 2 6 3 6
1 5 8 1 5 8 1 4 8 1 5 8
0 3 7 9 0 3 6 9 0 3 7 9 0 2 7 9
- R. H. Hardin, Jul 06 2012
- A231074 The number of possible ways to arrange the sums x_i + x_j (1 <= i < j <= n) of the items x_1 < x_2 <...< x_n in nondecreasing order.
1, 1, 1, 1, 2, 12, 244
nonn,more
- Vladimir Letsko, Mathematical Marathon, Problem 183 (in Russian)
- A231085 similiar, same author: a(1..7), more
- A131811 Number of symbolic sequences on n symbols that can be realized by the arrangement of the real roots of some polynomial of degree n and its derivatives.
- A213457 Intertwining numbers. (Formerly M1988)
1, 1, 2, 10, 148, 7384, 1380960, more