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 A238581 Number T(n,k) of equivalence classes of ways of placing k 2 X 2 tiles in an n X 9 rectangle under all symmetry operations of the rectangle; irregular triangle T(n,k), n>=2, 0<=k<=4*floor(n/2), read by rows. 21
 1, 4, 12, 10, 3, 1, 4, 24, 40, 22, 1, 8, 65, 230, 467, 476, 269, 70, 9, 1, 8, 109, 641, 2281, 4424, 4718, 2409, 473, 1, 12, 182, 1479, 7644, 24024, 47022, 56226, 41000, 17834, 4545, 625, 39, 1, 12, 258, 2762, 19347, 86536, 255552, 495547, 625705, 499314, 239254, 61732, 6533 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,2 LINKS Andrew Howroyd, Table of n, a(n) for n = 2..991 Christopher Hunt Gribble, C++ program EXAMPLE The first 4 rows of T(n,k) are: .\ k  0     1     2     3     4     5     6     7     8 n 2     1     4    12    10     3 3     1     4    24    40    22 4     1     8    65   230   467   476   269    70     9 5     1     8   109   641  2281  4424  4718  2409   473 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, A238582, A238583, A228169, A238586, A238592. Sequence in context: A273172 A307853 A247327 * A063608 A074258 A253137 Adjacent sequences:  A238578 A238579 A238580 * A238582 A238583 A238584 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(43) and beyond from Andrew Howroyd, May 29 2017 STATUS approved

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Last modified February 22 15:26 EST 2020. Contains 332137 sequences. (Running on oeis4.)