OFFSET
0,2
COMMENTS
All these numbers are even because there are the same number of matrices with positive and negative determinants. [T. D. Noe, Oct 08 2008]
MATHEMATICA
Table[cnt=0; Do[If[a*d-b*c != 0, cnt++ ], {a, 0, n}, {b, 0, n}, {c, 0, n}, {d, 0, n}]; cnt, {n, 0, 10}] (* T. D. Noe, Oct 08 2008 *)
CROSSREFS
KEYWORD
nonn,nice
AUTHOR
Ahmed Fares (ahmedfares(AT)my-deja.com), Jul 19 2001
EXTENSIONS
More terms from T. D. Noe, Oct 08 2008
STATUS
approved