Number of 2 X 2 matrices with all terms in {-n,..,0,..,n} and (sum of terms) = determinant.

Terms

a(0) =1a(1) =31a(2) =111a(3) =271a(4) =479a(5) =831a(6) =1167a(7) =1711a(8) =2239a(9) =2975a(10) =3631a(11) =4687a(12) =5407a(13) =6655a(14) =7759a(15) =9135a(16) =10367a(17) =12127a(18) =13231a(19) =15375a(20) =16991a(21) =19135a(22) =20879a(23) =23471a(24) =25215a(25) =27999a(26) =30319a(27) =33167a(28) =35359a(29) =39167