Number of 2 X 2 matrices having all terms in {1,...,n} and determinant >= n.

Terms

a(0) =0a(1) =3a(2) =19a(3) =69a(4) =181a(5) =411a(6) =785a(7) =1419a(8) =2334a(9) =3674a(10) =5478a(11) =7994a(12) =11093a(13) =15249a(14) =20347a(15) =26660a(16) =34253a(17) =43661a(18) =54463a(19) =67637a(20) =82614a(21) =100217a(22) =120415a(23) =143935a(24) =169815a(25) =199883a(26) =233505a(27) =271344a(28) =313103a(29) =360519