This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A062801 #7 Mar 15 2023 10:51:40
%S A062801 0,6,50,192,512,1126,2146,3760,6112,9430,13922,19888,27504,37206,
%T A062801 49202,63872,81600,102854,127874,157328,191440,230870,276114,327776,
%U A062801 386128,452118,526178,608960,701056,803430,916290,1040976,1177744,1327606
%N A062801 Number of 2 X 2 non-singular integer matrices with entries from {0,...,n}.
%C A062801 All these numbers are even because there are the same number of matrices with positive and negative determinants. [_T. D. Noe_, Oct 08 2008]
%t A062801 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 *)
%Y A062801 This sequence a(n) and A059306 give together all the 2 X 2 matrices with entries from {0, ..., n}, i.e. a(n) + A059306(n) = (n+1)^4.
%K A062801 nonn,nice
%O A062801 0,2
%A A062801 Ahmed Fares (ahmedfares(AT)my-deja.com), Jul 19 2001
%E A062801 More terms from _T. D. Noe_, Oct 08 2008