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 A221840 #22 Sep 20 2013 04:21:37
%S A221840 1,0,0,1,0,1,1,2,4,7
%N A221840 Number of sets of n squares providing dissections of a square.
%C A221840 It seems that a(11) = 16 and a(12) = 30. [_Vladimir Letsko_, Sep 17 2013]
%H A221840 <a href="http://www-old.fizmat.vspu.ru/doku.php?id=marathon:problem_152"> Mathematical Marathon, Problem 152</a> (in Russian)
%e A221840 a(8) = 2 as there are two sets of 8 squares which tile a unit square, namely {1(0.75X0.75), 7(0.25X0.25)} and {1(0.6X0.6), 3(0.4X0.4), 4(0.2X0.2)}.
%Y A221840 Cf. A221841, A005670.
%K A221840 nonn,more
%O A221840 1,8
%A A221840 _Geoffrey H. Morley_, Jan 26 2013
%E A221840 a(10) corrected by _Geoffrey H. Morley_, Aug 02 2013