This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A238189 #34 May 30 2017 12:14:28 %S A238189 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, %T A238189 1,8,49,139,204,145,54,8,1,1,8,65,230,467,476,269,70,9,1,10,85,377, %U A238189 961,1348,1080,472,111,12,1,1,10,106,552,1767,3188,3454,2156 %N 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. %H A238189 Andrew Howroyd, <a href="/A238189/b238189.txt">Table of n, a(n) for n = 2..967</a> (terms n=2..127 from Christopher Hunt Gribble) %H A238189 Christopher Hunt Gribble, <a href="/A238009/a238009_1.cpp.txt">C++ program</a> %e A238189 The first 10 rows of T(n,k) are: %e A238189 k 0 1 2 3 4 5 6 7 8 9 10 %e A238189 n %e A238189 2 1 2 1 %e A238189 3 1 2 2 %e A238189 4 1 4 7 3 1 %e A238189 5 1 4 13 10 4 %e A238189 6 1 6 23 33 22 6 1 %e A238189 7 1 6 34 68 72 30 6 %e A238189 8 1 8 49 139 204 145 54 8 1 %e A238189 9 1 8 65 230 467 476 269 70 9 %e A238189 10 1 10 85 377 961 1348 1080 472 111 12 1 %e A238189 11 1 10 106 552 1767 3188 3454 2156 779 140 12 %o A238189 (C++) See Gribble link. %Y A238189 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. %K A238189 tabf,nonn %O A238189 2,2 %A A238189 _Christopher Hunt Gribble_, Feb 19 2014 %E A238189 Terms corrected and extended by _Christopher Hunt Gribble_, Apr 25 2015