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Number of pairs of orthogonal (-2,5) vectors of length 7*n.
1

%I #7 Sep 06 2013 02:05:08

%S 378,5133128,81705087744,983771662124160,13027612739061516288,

%T 180842352214339004973056,2505372582582745606695616512,

%U 35065654463193295271305370959872,495605164965018396615832445084368896

%N Number of pairs of orthogonal (-2,5) vectors of length 7*n.

%C Row 8 of A225987.

%H R. H. Hardin, <a href="/A225994/b225994.txt">Table of n, a(n) for n = 1..78</a>

%e Some solutions for n=1

%e .-2..5...-2..5...-2..5...-2..5....5..5...-2..5....5..5....5..5...-2..5...-2..5

%e .-2..5....5..5....5.-2...-2..5....5..5....5..5...-2..5...-2..5....5..5....5.-2

%e ..5..5...-2..5....5.-2....5.-2...-2..5....5.-2....5.-2....5.-2....5.-2....5..5

%e .-2..5...-2..5....5.-2....5.-2...-2..5....5..5...-2..5....5..5....5.-2....5..5

%e ..5.-2....5.-2....5.-2....5..5....5.-2....5.-2...-2..5...-2..5....5.-2...-2..5

%e ..5..5....5..5....5..5....5.-2...-2..5....5.-2....5.-2....5.-2....5.-2...-2..5

%e ..5.-2....5.-2....5..5....5..5...-2..5...-2..5....5..5....5.-2....5..5...-2..5

%K nonn

%O 1,1

%A _R. H. Hardin_, May 22 2013