A225990 Number of pairs of orthogonal (-2,3) vectors of length 5*n.

60, 48720, 41801760, 36951200000, 33792065269760, 31520952625612800, 29804588641610956800, 28466071692659367936000, 27397648707462915867279360, 26530254119576872937974661120, 25817362047962660055225414451200

Offset: 1

Author

R. H. Hardin, May 22 2013

Keywords

• nonn

Comments

Row 4 of A225987.

Examples

			Some solutions for n=1
.-2..3...-2..3...-2..3....3..3...-2.-2...-2..3...-2.-2...-2.-2...-2..3...-2..3
.-2..3....3.-2....3..3...-2..3...-2..3...-2..3...-2..3...-2..3....3.-2....3.-2
..3..3....3..3...-2..3...-2..3...-2.-2...-2..3...-2.-2...-2.-2....3..3...-2..3
.-2..3....3..3....3..3....3..3...-2..3....3..3...-2.-2....3.-2....3..3....3..3
..3..3....3.-2...-2..3....3.-2...-2.-2....3..3....3.-2...-2.-2...-2..3....3..3
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..115