A286920 Triangle read by rows: T(n,m) is the number of pattern classes in the (n,m)-rectangular grid with 9 colors and n>=m, two patterns are in the same class if one of them can be obtained by a reflection or 180-degree rotation of the other.

1, 1, 9, 1, 45, 1701, 1, 405, 134865, 97135605, 1, 3321, 10766601, 70618411521, 463255079498001, 1, 29889, 871858485, 51473762336565, 3039416437115008521, 179474497026544179696969, 1, 266085, 70607782701, 37523729625344145, 19941610769429949618201, 10597789568841677482963905405, 5632099886234793715531013441442501

Offset

0,3

Comments

Computed using Burnsides orbit-counting lemma.

Links

María Merino, Rows n=0..33 of triangle, flattened

M. Merino and I. Unanue, Counting squared grid patterns with Pólya Theory, EKAIA, 34 (2018), 289-316 (in Basque).

Formula

For even n and m: T(n,m) = (9^(m*n) + 3*9^(m*n/2))/4;

for even n and odd m: T(n,m) = (9^(m*n) + 9^((m*n+n)/2) + 2*9^(m*n/2))/4;

for odd n and even m: T(n,m) = (9^(m*n) + 9^((m*n+m)/2) + 2*9^(m*n/2))/4;

for odd n and m: T(n,m) = (9^(m*n) + 9^((m*n+n)/2) + 9^((m*n+m)/2) + 9^((m*n+1)/2))/4.

Example

Triangle begins:
==========================================================
n\m |   0   1     2         3              4
----|-----------------------------------------------------
0   |   1
1   |   1   9
2   |   1   45    1701
3   |   1   405   134865    97135605
4   |   1   3321  10766601  70618411521    463255079498001
...

Crossrefs

Cf. A225910, A283432, A283433, A283434, A286893, A286895, A286919.

Sequence in context: A283043 A283016 A050303 * A306557 A283060 A283082

Adjacent sequences: A286917 A286918 A286919 * A286921 A286922 A286923

Keyword

nonn,tabl

Author

María Merino, Imanol Unanue, Yosu Yurramendi, May 16 2017

Status

approved