A192709 Number of 9X2 integer matrices with each row summing to zero, row elements in nondecreasing order, rows in lexicographically nondecreasing order, and the sum of squares of the elements <= 2*n^2 (number of collections of 9 zero-sum 2-vectors with total modulus squared not more than 2*n^2, ignoring vector and component permutations).

2, 6, 19, 46, 108, 231, 460, 872, 1581, 2737, 4607, 7508, 11904, 18426, 27989, 41631, 60856, 87536, 124153, 173696, 239976, 327657, 442880, 592595, 785351, 1031659, 1344609, 1738831, 2232241, 2845802, 3605355, 4538949, 5681318, 7071215, 8756412

Offset: 1

Author

R. H. Hardin Jul 07 2011

Keywords

• nonn

Comments

Column (9,2,n) of A192710

Examples

			Some solutions for 9X2 <= 2*4^2
.-2..2...-3..3...-2..2...-2..2...-1..1...-2..2...-2..2....0..0...-3..3...-1..1
.-1..1...-2..2...-2..2...-2..2...-1..1...-1..1...-1..1....0..0...-2..2...-1..1
.-1..1...-1..1...-2..2...-2..2...-1..1...-1..1...-1..1....0..0...-1..1...-1..1
.-1..1...-1..1...-1..1...-1..1....0..0...-1..1...-1..1....0..0...-1..1...-1..1
.-1..1...-1..1....0..0...-1..1....0..0...-1..1...-1..1....0..0....0..0...-1..1
.-1..1....0..0....0..0...-1..1....0..0....0..0...-1..1....0..0....0..0...-1..1
.-1..1....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0...-1..1
..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0...-1..1
..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0...-1..1
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..102