Number of 3 X 3 0..n arrays with positive determinant.

Terms

a(0) =87a(1) =6396a(2) =106449a(3) =862194a(4) =4680741a(5) =19121763a(6) =64776942a(7) =188565579a(8) =490027068a(9) =1160214360a(10) =2549098734a(11) =5247510432a(12) =10247764287a(13) =19091929404a(14) =34162836240a(15) =59000910075a(16) =98778606894a(17) =160758105174a(18) =255224874669a(19) =396052831464