%I #15 Dec 17 2016 03:54:33

%S 1,1,1,5,3,130,7570,355293682

%N Number of nonisomorphic orthogonal arrays OA(4n,4n-1,2,2).

%C Equivalently, number of 3-(4*n,2*n,n-1) designs.

%D A. S. Hedayat, N. J. A. Sloane and J. Stufken, Orthogonal Arrays, Springer-Verlag, NY, 1999, see Table 7.37 page 165.

%H <a href="/index/Ha#Hadamard">Index entries for sequences related to Hadamard matrices</a>

%Y Cf. A007299.

%K nonn,nice,hard,more

%O 1,4

%A _N. J. A. Sloane_

%E a(7) computed by _N. J. A. Sloane_

%E a(8) from _Brendan McKay_, Feb 11 2012