A225987 T(n,k)=Number of pairs of orthogonal (-x,y) vectors of length k*(x+y), where x/y is the n-th rational <= 1, ordered first by y and then x, e.g. 1/1, 1/2, 1/3, 2/3, 1/4, 3/4 ...

4, 48, 9, 640, 390, 20, 8960, 20160, 3192, 60, 129024, 1106424, 652784, 48720, 45, 1892352, 62606544, 134432480, 41801760, 26010, 420, 28114944, 3611217792, 28244153600, 36951200000, 21594300, 8168160, 102, 421724160, 211096262400

Offset: 1

Author

R. H. Hardin, May 22 2013

Keywords

• nonn
• tabl

Comments

Table starts

..4....48......640........8960.........129024...........1892352

..9...390....20160.....1106424.......62606544........3611217792

.20..3192...652784...134432480....28244153600.....6052498776192

.60.48720.41801760.36951200000.33792065269760.31520952625612800

.45.26010.21594300.15593341800.11432293516320..8690522384325600

Examples

			Some solutions for n=1 k=4
.-1..1....1..1...-1.-1...-1.-1...-1..1....1..1...-1..1...-1.-1...-1.-1...-1..1
..1..1...-1.-1...-1..1...-1..1....1..1...-1..1...-1.-1...-1..1...-1..1...-1.-1
.-1..1...-1..1....1..1...-1.-1...-1..1....1.-1....1.-1...-1.-1....1.-1....1.-1
.-1.-1...-1.-1....1.-1...-1.-1....1..1...-1.-1....1.-1...-1..1....1.-1....1.-1
..1.-1....1.-1...-1.-1....1.-1...-1.-1...-1.-1....1..1...-1..1...-1..1...-1.-1
..1.-1...-1..1....1..1....1..1...-1..1....1.-1....1.-1...-1.-1...-1.-1...-1.-1
..1..1....1..1...-1..1....1.-1....1.-1....1.-1....1..1....1..1...-1.-1...-1.-1
..1..1....1.-1...-1..1...-1..1...-1.-1...-1.-1....1..1....1.-1...-1.-1....1.-1
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..1056

Crossrefs

Row 1 is A098402.