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 A165632 #4 Jul 14 2012 11:32:31
%S A165632 70,88,96,108,126,130,140,150,154,160,176,180,192,198,204,208,216,228,
%T A165632 234,238,240,250,252,260,266,270,280,286,294,300,304,308,320,322,330,
%U A165632 336,340,348,352,360,368,372,374,378,384,390,396,400,408,414,416,418
%N A165632 Sizes of tatami-free rooms.
%C A165632 Even numbers s such that some rectangle of size s=r*c (r,c positive integers) cannot be tiled with tatamis of size 1x2 such that not more than 3 tatamis meet at any point.
%C A165632 The number of different rectangles of size a(n) which have this property is given in A165633(n).
%H A165632 Project Euler, <a href="http://projecteuler.net/index.php?section=problems&id=256">Problem 256: Tatami-Free Rooms</a>
%F A165632 A165632 = { r*c in 2Z | A068920(r,c)=0 }
%e A165632 a(1)=70 because the rectangle of size 7x10 is the smallest that cannot be filled with 2x1 tiles without having 4 tiles meet in some point.
%Y A165632 Cf. A068920.
%K A165632 nonn
%O A165632 1,1
%A A165632 _M. F. Hasler_, Sep 26 2009