Number of 4X4 0..n matrices whose square is also a 0..n matrix.

Terms

a(0) =6327a(1) =120133a(2) =604639a(3) =3510112a(4) =9131098a(5) =29365738a(6) =56599992a(7) =127113628a(8) =255379242a(9) =499365458a(10) =784233528a(11) =1531915046a(12) =2261261860a(13) =3473439982a(14) =5267581848a(15) =8552671195a(16) =11581885709a(17) =17881607889a(18) =23603815011a(19) =34808081571