Number of 2 X 2 singular integer matrices with elements from {0,...,n}.

Terms

a(0) =1a(1) =10a(2) =31a(3) =64a(4) =113a(5) =170a(6) =255a(7) =336a(8) =449a(9) =570a(10) =719a(11) =848a(12) =1057a(13) =1210a(14) =1423a(15) =1664a(16) =1921a(17) =2122a(18) =2447a(19) =2672a(20) =3041a(21) =3386a(22) =3727a(23) =4000a(24) =4497a(25) =4858a(26) =5263a(27) =5696a(28) =6225a(29) =6570