A238582 Number T(n,k) of equivalence classes of ways of placing k 3 X 3 tiles in an n X 9 rectangle under all symmetry operations of the rectangle; irregular triangle T(n,k), n>=3, 0<=k<=2*floor(n/3), read by rows.

1, 4, 6, 1, 1, 4, 12, 3, 1, 8, 28, 10, 1, 8, 54, 82, 49, 8, 1, 1, 12, 95, 283, 311, 91, 10, 1, 12, 146, 647, 1118, 451, 68, 1, 16, 212, 1300, 3380, 3076, 1200, 209, 20, 1, 1, 16, 288, 2260, 8443, 13336, 9364, 2819, 387, 20

Offset: 3

Author

Christopher Hunt Gribble, Mar 01 2014

Keywords

• tabf
• nonn

Examples

			The first 9 rows of T(n,k) are:
.\ k  0     1     2     3     4     5     6     7     8     9
n
3     1     4     6     1
4     1     4    12     3
5     1     8    28    10
6     1     8    54    82    49     8     1
7     1    12    95   283   311    91    10
8     1    12   146   647  1118   451    68
9     1    16   212  1300  3380  3076  1200   209    20     1
10    1    16   288  2260  8443 13336  9364  2819   387    20
11    1    20   379  3709 18203 42412 44599 19051  3682   282
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 3..989
• Christopher Hunt Gribble, C++ program

Crossrefs

Cf. A034851, A226048, A102541, A226290, A238009, A228570, A225812, A238189, A238190, A228572, A228022, A231145, A231473, A231568, A232440, A228165, A238550-A238552, A228166, A238555, A238556, A228167, A238557-A238559, A228168, A238581, A238583, A228169, A238586, A238592.

Extensions

Terms corrected and xrefs updated by Christopher Hunt Gribble, Apr 27 2015

Terms a(46) and beyond from Andrew Howroyd, May 29 2017