A238556 Number T(n,k) of equivalence classes of ways of placing k 3 X 3 tiles in an n X 7 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, 3, 2, 1, 3, 4, 1, 6, 9, 1, 6, 21, 13, 4, 1, 9, 39, 53, 23, 1, 9, 64, 128, 87, 1, 12, 95, 283, 311, 91, 10, 1, 12, 133, 521, 891, 543, 106, 1, 15, 177, 917, 2118, 2030, 646, 1, 15, 228, 1444, 4424, 6000, 3295, 456, 25, 1, 18, 285, 2207, 8408, 15484, 13106, 4322, 473

Offset: 3

Author

Christopher Hunt Gribble, Feb 28 2014

Keywords

• tabf
• nonn

Examples

			The first 5 rows of T(n,k) are:
./ k    0      1      2      3      4      5      6
n
3       1      3      2
4       1      3      4
5       1      6      9
6       1      6     21     13      4
7       1      9     39     53     23
8       1      9     64    128     87
9       1     12     95    283    311     91     10
10      1     12    133    521    891    543    106
11      1     15    177    917   2118   2030    646
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 3..971
• 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, A228167, A238557-A238559, A228168, A238581-A238583, A228169, A238586, A238592.

Extensions

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

Terms a(48) and beyond by Andrew Howroyd, May 29 2017