The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 60th year, we have over 367,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A174686 Number of equivalence classes of 3 X 3 matrices filled with n colors so that no two rotations are identical. 0
 120, 4860, 65280, 487500, 2517480, 10084200, 33546240, 96840360, 249975000, 589446660, 1289882880, 2651032020, 5165127240, 9610650000, 17179607040, 29646614160, 49589350200, 80671305420, 127999200000, 198568990620, 301816016040, 450286556280, 660449894400 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS Each class contains a set of 4 matrices so that all of them can be obtained by successive rotation but no two are identical. LINKS Table of n, a(n) for n=2..24. FORMULA 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. PROG (PARI) a(n) = (n^9 - n^5)/4 \\ Michel Marcus, Mar 04 2013 CROSSREFS Sequence in context: A111155 A283344 A223754 * A140907 A072419 A246193 Adjacent sequences: A174683 A174684 A174685 * A174687 A174688 A174689 KEYWORD nonn AUTHOR Srikanth K S, Mar 27 2010 EXTENSIONS More terms from Michel Marcus, Mar 04 2013 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 2 19:08 EST 2023. Contains 367525 sequences. (Running on oeis4.)