A243866 Table T(n,k), n>=1, k>=1, read by antidiagonals: T(n,k) = number of equivalence classes of ways of placing one 1 X 1 tile in an n X k rectangle under all symmetry operations of the rectangle.

1, 1, 1, 2, 1, 2, 2, 2, 2, 2, 3, 2, 4, 2, 3, 3, 3, 4, 4, 3, 3, 4, 3, 6, 4, 6, 3, 4, 4, 4, 6, 6, 6, 6, 4, 4, 5, 4, 8, 6, 9, 6, 8, 4, 5, 5, 5, 8, 8, 9, 9, 8, 8, 5, 5, 6, 5, 10, 8, 12, 9, 12, 8, 10, 5, 6, 6, 6, 10, 10, 12, 12, 12, 12, 10, 10, 6, 6, 7, 6, 12, 10, 15

Offset: 1

Author

Christopher Hunt Gribble, Jun 19 2014

Keywords

• tabl
• nonn

Comments

It appears that the number of equivalence classes of ways of placing one m X m tile in an n X k rectangle under all symmetry operations of the rectangle is T(n-m+1,k-m+1) for m >= 2, n >= m and k >= m, and zero otherwise. - Christopher Hunt Gribble, Oct 17 2014

The sum over each antidiagonal of A243866

= Sum_{j=1..n}(2*j + 1 - (-1)^j)*(2*(n - j + 1) + 1 - (-1)^(n - j + 1))/16

= (n + 2)*(2*n^2 + 8*n + 3 - 3*(-1)^n)/48

- see A006918. - Christopher Hunt Gribble, Apr 01 2015

Examples

			T(n,k) for 1<=n<=11 and 1<=k<=11 is:
    k    1    2    3    4    5    6    7    8    9   10   11 ...
.n
.1       1    1    2    2    3    3    4    4    5    5    6
.2       1    1    2    2    3    3    4    4    5    5    6
.3       2    2    4    4    6    6    8    8   10   10   12
.4       2    2    4    4    6    6    8    8   10   10   12
.5       3    3    6    6    9    9   12   12   15   15   18
.6       3    3    6    6    9    9   12   12   15   15   18
.7       4    4    8    8   12   12   16   16   20   20   24
.8       4    4    8    8   12   12   16   16   20   20   24
.9       5    5   10   10   15   15   20   20   25   25   30
10       5    5   10   10   15   15   20   20   25   25   30
11       6    6   12   12   18   18   24   24   30   30   36
...
		

Links

• Christopher Hunt Gribble, Table of n, a(n) for n = 1..9870

Crossrefs

Cf. A034851, A226048, A226290, A225812, A228022, A228165, A228166, A006918, A244306, A244307, A248011, A248016, A248059, A248060, A248017, A248027.

Programs

Maple

b := proc (n,k);
floor((1/2)*n+1/2)*floor((1/2)*k+1/2)
end proc;
seq(seq(b(n, k-n+1), n = 1 .. k), k = 1 .. 140);

Formula

Empirically,

T(n,k) = floor((n+1)/2)*floor((k+1)/2)

= (2*n+1-(-1)^n)*(2*k+1-(-1)^k)/4;

T(n,1) = A034851(n,1);

T(n,2) = A226048(n,1);

T(n,3) = A226290(n,1);

T(n,4) = A225812(n,1);

T(n,5) = A228022(n,1);

T(n,6) = A228165(n,1);

T(n,7) = A228166(n,1). - Christopher Hunt Gribble, May 01 2015

Extensions

Terms corrected by Christopher Hunt Gribble, Mar 27 2015