Number of 2 X 2 matrices with all elements in {1,2,...,n} and determinant in {-1,0,1}.

Terms

a(0) =0a(1) =1a(2) =10a(3) =31a(4) =60a(5) =105a(6) =154a(7) =223a(8) =300a(9) =393a(10) =490a(11) =607a(12) =748a(13) =889a(14) =1034a(15) =1215a(16) =1404a(17) =1593a(18) =1818a(19) =2031a(20) =2300a(21) =2569a(22) =2810a(23) =3071a(24) =3436a(25) =3753a(26) =4042a(27) =4399a(28) =4796a(29) =5129