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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. 21
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,2

LINKS

Andrew Howroyd, Table of n, a(n) for n = 3..971

Christopher Hunt Gribble, C++ program

EXAMPLE

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

PROG

(C++) See Gribble link.

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.

Sequence in context: A023636 A205838 A238583 * A102288 A081248 A214636

Adjacent sequences:  A238553 A238554 A238555 * A238557 A238558 A238559

KEYWORD

tabf,nonn

AUTHOR

Christopher Hunt Gribble, Feb 28 2014

EXTENSIONS

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

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

STATUS

approved

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Last modified February 20 17:04 EST 2020. Contains 332080 sequences. (Running on oeis4.)