A192714 Number of 13X2 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 13 zero-sum 2-vectors with total modulus squared not more than 2*n^2, ignoring vector and component permutations).

2, 6, 19, 55, 140, 331, 732, 1533, 3055, 5857, 10824, 19386, 33743, 57293, 95044, 154445, 246197, 385697, 594416, 902641, 1351643, 1998191, 2918046, 4213843, 6019994, 8515367, 11930845, 16568416, 22815114, 31168260, 42253487, 56871045

Offset: 1

Author

R. H. Hardin Jul 07 2011

Keywords

• nonn

Comments

Column (13,2,n) of A192710

Examples

			Some solutions for 13X2 <= 2*4^2
.-3..3...-2..2...-2..2...-2..2...-2..2...-2..2...-3..3...-2..2...-2..2...-3..3
.-1..1....0..0...-2..2...-2..2...-2..2...-2..2...-1..1...-1..1...-1..1...-2..2
.-1..1....0..0...-1..1...-2..2...-2..2....0..0...-1..1...-1..1...-1..1...-1..1
.-1..1....0..0...-1..1...-1..1...-1..1....0..0...-1..1...-1..1...-1..1...-1..1
.-1..1....0..0...-1..1...-1..1...-1..1....0..0...-1..1...-1..1...-1..1....0..0
.-1..1....0..0...-1..1...-1..1....0..0....0..0...-1..1...-1..1...-1..1....0..0
.-1..1....0..0...-1..1...-1..1....0..0....0..0....0..0...-1..1...-1..1....0..0
..0..0....0..0...-1..1....0..0....0..0....0..0....0..0...-1..1...-1..1....0..0
..0..0....0..0...-1..1....0..0....0..0....0..0....0..0...-1..1....0..0....0..0
..0..0....0..0...-1..1....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....0..0....0..0....0..0
..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0
..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..62