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 A238551 #22 May 29 2017 21:19:06 %S A238551 1,2,1,1,2,2,1,4,4,1,4,11,3,1,1,6,21,13,4,1,6,36,32,13,1,8,54,82,49,8, %T A238551 1,1,8,77,165,151,44,6,1,10,103,319,382,173,31,1,10,134,530,867,559, %U A238551 164,12,1,1,12,168,852,1789,1632,705,119,9 %N A238551 Number T(n,k) of equivalence classes of ways of placing k 3 X 3 tiles in an n X 6 rectangle under all symmetry operations of the rectangle; irregular triangle T(n,k), n>=3, 0<=k<=2*floor(n/3), read by rows. %H A238551 Andrew Howroyd, <a href="/A238551/b238551.txt">Table of n, a(n) for n = 3..971</a> %H A238551 Christopher Hunt Gribble, <a href="/A238009/a238009_1.cpp.txt">C++ program</a> %e A238551 The first 12 rows of T(n,k) are: %e A238551 .\ k 0 1 2 3 4 5 6 7 8 %e A238551 n %e A238551 3 1 2 1 %e A238551 4 1 2 2 %e A238551 5 1 4 4 %e A238551 6 1 4 11 3 1 %e A238551 7 1 6 21 13 4 %e A238551 8 1 6 36 32 13 %e A238551 9 1 8 54 82 49 8 1 %e A238551 10 1 8 77 165 151 44 6 %e A238551 11 1 10 103 319 382 173 31 %e A238551 12 1 10 134 530 867 559 164 12 1 %e A238551 13 1 12 168 852 1789 1632 705 119 9 %e A238551 14 1 12 207 1255 3409 4074 2406 618 66 %o A238551 (C++) See Gribble link. %Y A238551 Cf. A034851, A226048, A102541, A226290, A238009, A228570, A225812, A238189, A238190, A228572, A228022, A231145, A231473, A231568, A232440, A228165, A238550, A238552, A228166, A238555, A238556, A228167, A238557, A238558, A238559, A228168, A238581, A238582, A238583, A228169, A238586, A238592. %K A238551 tabf,nonn %O A238551 3,2 %A A238551 _Christopher Hunt Gribble_, Feb 28 2014 %E A238551 Terms corrected and xrefs updated by _Christopher Hunt Gribble_, Apr 27 2015 %E A238551 Terms a(57) and beyond from _Andrew Howroyd_, May 29 2017