A225989 Number of pairs of orthogonal (-1,3) vectors of length 4*n.

20, 3192, 652784, 134432480, 28244153600, 6052498776192, 1314942362273280, 288501497813552640, 63776322167821168640, 14182989297327325110272, 3169467786802943379238912, 711136363409644515952173056

Offset: 1

Author

R. H. Hardin, May 22 2013

Keywords

• nonn

Comments

Row 3 of A225987.

Examples

			Some solutions for n=1
.-1..3...-1..3....3..3...-1..3...-1..3...-1..3...-1..3...-1.-1....3..3...-1..3
..3..3...-1..3...-1..3....3..3...-1..3....3.-1...-1..3...-1.-1...-1..3....3.-1
.-1..3....3..3...-1..3....3.-1....3.-1....3..3...-1..3...-1.-1....3.-1....3..3
..3.-1....3.-1....3.-1...-1..3....3..3...-1..3....3..3...-1..3....3.-1....3.-1
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..145