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 A238189 Number T(n,k) of equivalence classes of ways of placing k 2 X 2 tiles in an n X 4 rectangle under all symmetry operations of the rectangle; irregular triangle T(n,k), n>=2, 0<=k<=n-n%2, read by rows. 21
 1, 2, 1, 1, 2, 2, 1, 4, 7, 3, 1, 1, 4, 13, 10, 4, 1, 6, 23, 33, 22, 6, 1, 1, 6, 34, 68, 72, 30, 6, 1, 8, 49, 139, 204, 145, 54, 8, 1, 1, 8, 65, 230, 467, 476, 269, 70, 9, 1, 10, 85, 377, 961, 1348, 1080, 472, 111, 12, 1, 1, 10, 106, 552, 1767, 3188, 3454, 2156 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,2 LINKS Andrew Howroyd, Table of n, a(n) for n = 2..967 (terms n=2..127 from Christopher Hunt Gribble) Christopher Hunt Gribble, C++ program EXAMPLE The first 10 rows of T(n,k) are:   k  0     1     2     3     4     5     6     7     8     9    10 n 2    1     2     1 3    1     2     2 4    1     4     7     3     1 5    1     4    13    10     4 6    1     6    23    33    22     6     1 7    1     6    34    68    72    30     6 8    1     8    49   139   204   145    54     8     1 9    1     8    65   230   467   476   269    70     9 10   1    10    85   377   961  1348  1080   472   111    12     1 11   1    10   106   552  1767  3188  3454  2156   779   140    12 PROG (C++) See Gribble link. CROSSREFS Cf. A034851, A226048, A102541, A226290, A238009, A228570, A225812, A238190, A228572, A228022, A231145, A231473, A231568, A232440, A228165, A238550, A238551, A238552, A228166, A238555, A238556, A228167, A238557, A238558, A238559, A228168, A238581, A238582, A238583, A228169, A238586, A238592. Sequence in context: A220188 A238551 A289676 * A029256 A216501 A217463 Adjacent sequences:  A238186 A238187 A238188 * A238190 A238191 A238192 KEYWORD tabf,nonn AUTHOR Christopher Hunt Gribble, Feb 19 2014 EXTENSIONS Terms corrected and extended by Christopher Hunt Gribble, Apr 25 2015 STATUS approved

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Last modified February 22 15:32 EST 2020. Contains 332137 sequences. (Running on oeis4.)