A279415 Triangle read by rows: T(n,k), n>=k>=1, is the number of right isosceles triangles with integral coordinates that have a bounding box of size n X k.

0, 0, 4, 0, 2, 4, 0, 0, 4, 4, 0, 0, 2, 4, 4, 0, 0, 0, 4, 4, 4, 0, 0, 0, 2, 4, 4, 4, 0, 0, 0, 0, 4, 4, 4, 4, 0, 0, 0, 0, 2, 4, 4, 4, 4, 0, 0, 0, 0, 0, 4, 4, 4, 4, 4, 0, 0, 0, 0, 0, 2, 4, 4, 4, 4, 4, 0, 0, 0, 0, 0, 0, 4, 4, 4, 4, 4, 4, 0, 0, 0, 0, 0, 0, 2, 4, 4

Offset: 1

Author

Lars Blomberg, Feb 27 2017

Keywords

• nonn
• tabl

Examples

			Triangle begins:
0
0,4
0,2,4
0,0,4,4
0,0,2,4,4
0,0,0,4,4,4
0,0,0,2,4,4,4
0,0,0,0,4,4,4,4
0,0,0,0,2,4,4,4,4
0,0,0,0,0,4,4,4,4,4
0,0,0,0,0,2,4,4,4,4,4
0,0,0,0,0,0,4,4,4,4,4,4
0,0,0,0,0,0,2,4,4,4,4,4,4
-------
The right angle is 'o'.
For n=4, k=3:
x...   .o..   ..o.   ...x
...x   ...x   x...   x...
.o..   x...   ...x   ..o.
So T(4,3)=4
-------
For n=4, k=4:
o..x   x..o   x...   ...x
....   ....   ....   ....
....   ....   ....   ....
x...   ...x   o..x   x..o
So T(4,4)=4
		

Links

• Lars Blomberg, Table of n, a(n) for n = 1..9870 (the first 140 rows)

Crossrefs

Cf. A187452.

See A280639 for obtuse isosceles triangles.

See A279418 for acute isosceles triangles.

See A279413 for all isosceles triangles.

See A279433 for all right triangles.

See A280652 for all obtuse triangles.

See A280653 for all acute triangles.

See A279432 for all triangles.