OFFSET
1,2
COMMENTS
It would be nice to have a formula. - N. J. A. Sloane, Jun 29 2016
Place all bounding boxes of A279433 that will fit into the n X n grid in all possible positions, and the proper rectangles in two orientations: a(n) = sum(i=1..n, sum(j=1..i, k * (n-i+1) * (n-j+1) * A279433(i,j) where k=1 when i=j and k=2 otherwise. - Lars Blomberg, Mar 01 2017
LINKS
Lars Blomberg, Table of n, a(n) for n = 1..10000 (the first 184 terms from R. H. Hardin)
EXAMPLE
For n=2 if the four points are labeled
ab
cd
then the right triangles are abc, abd, acd, bcd,
so a(2)=4.
For n=3, label the points
abc
def
ghi
The right triangles are: abd (4*4 ways), acg (4 ways), acd and adf (8 ways each), ace and dbf (4 ways each), for a total of a(3) = 44. - N. J. A. Sloane, Jun 30 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
John W. Layman, Nov 30 2002
EXTENSIONS
a(1) corrected by Lars Blomberg, Mar 01 2017
STATUS
approved