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 A174686 #11 Mar 04 2013 10:48:25 %S A174686 120,4860,65280,487500,2517480,10084200,33546240,96840360,249975000, %T A174686 589446660,1289882880,2651032020,5165127240,9610650000,17179607040, %U A174686 29646614160,49589350200,80671305420,127999200000,198568990620,301816016040,450286556280,660449894400 %N A174686 Number of equivalence classes of 3 X 3 matrices filled with n colors so that no two rotations are identical. %C A174686 Each class contains a set of 4 matrices so that all of them can be obtained by successive rotation but no two are identical. %F A174686 a(n) = (n^9 - n^(floor(9/2) + 1))/4. More generally for any m X m matrix f(n,m) = (n^(m^2) - n^(m^2/2))/4 if m is even, and f(n,m) = (n^(m^2) - n^(floor(m^2/2)+1))/4 if m is odd. %o A174686 (PARI) a(n) = (n^9 - n^5)/4 \\ _Michel Marcus_, Mar 04 2013 %K A174686 nonn %O A174686 2,1 %A A174686 _Srikanth K S_, Mar 27 2010 %E A174686 More terms from _Michel Marcus_, Mar 04 2013