OFFSET
1,3
LINKS
E. Fusy, D. Poulalhon, and G. Schaeffer, Bijective counting of plane bipolar orientations, El. Notes Discr. Math. 29 (2007) 283-287.
FORMULA
T(i,j) = T(j,i) = 2*(i+j-2)!*(i+j-1)!*(i+j)!/((i-1)!*i!*(i+1)!*(j-1)!*j!*(j+1)!).
EXAMPLE
The triangle starts in row 1 as
1;
1, 4;
1, 10, 50;
1, 20, 175, 980;
1, 35, 490, 4116, 24696;
1, 56, 1176, 14112, 116424, 731808;
1, 84, 2520, 41580, 457380, 3737448, 24293412;
1, 120, 4950, 108900, 1557270, 16195608, 131589315, 877262100;
MAPLE
CROSSREFS
KEYWORD
AUTHOR
R. J. Mathar, Feb 25 2018
STATUS
approved