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 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. 12
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,2 LINKS Andrew Howroyd, Table of n, a(n) for n = 3..989 Christopher Hunt Gribble, C++ program EXAMPLE 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 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, A238556, A228167, A238557-A238559, A228168, A238581, A238583, A228169, A238586, A238592. Sequence in context: A262562 A107951 A019646 * A154748 A190282 A164833 Adjacent sequences:  A238579 A238580 A238581 * A238583 A238584 A238585 KEYWORD tabf,nonn AUTHOR Christopher Hunt Gribble, Mar 01 2014 EXTENSIONS Terms corrected and xrefs updated by Christopher Hunt Gribble, Apr 27 2015 Terms a(46) and beyond from Andrew Howroyd, May 29 2017 STATUS approved

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Last modified January 22 02:06 EST 2020. Contains 331133 sequences. (Running on oeis4.)