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%I A238581 #18 May 29 2017 21:14:11
%S A238581 1,4,12,10,3,1,4,24,40,22,1,8,65,230,467,476,269,70,9,1,8,109,641,
%T A238581 2281,4424,4718,2409,473,1,12,182,1479,7644,24024,47022,56226,41000,
%U A238581 17834,4545,625,39,1,12,258,2762,19347,86536,255552,495547,625705,499314,239254,61732,6533
%N 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.
%H A238581 Andrew Howroyd, <a href="/A238581/b238581.txt">Table of n, a(n) for n = 2..991</a>
%H A238581 Christopher Hunt Gribble, <a href="/A238009/a238009_1.cpp.txt">C++ program</a>
%e A238581 The first 4 rows of T(n,k) are:
%e A238581 .\ k  0     1     2     3     4     5     6     7     8
%e A238581 n
%e A238581 2     1     4    12    10     3
%e A238581 3     1     4    24    40    22
%e A238581 4     1     8    65   230   467   476   269    70     9
%e A238581 5     1     8   109   641  2281  4424  4718  2409   473
%o A238581 (C++) See Gribble link.
%Y A238581 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.
%K A238581 tabf,nonn
%O A238581 2,2
%A A238581 _Christopher Hunt Gribble_, Mar 01 2014
%E A238581 Terms corrected and xrefs updated by _Christopher Hunt Gribble_, Apr 27 2015
%E A238581 Terms a(43) and beyond from _Andrew Howroyd_, May 29 2017

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