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 A270069 #6 Feb 06 2017 12:33:59 %S A270069 1,19,13413,5952243,2626057921,1162378878394,517174361985073, %T A270069 229681994753502100,101965922336345576219,45283517791861200639757, %U A270069 20109634299824273864511862,8930062817269356408791188106,3965614916098256915340694883017,1761030770921730133912679646624228 %N A270069 Number of tilings of a 9 X n rectangle using monominoes and trominoes of any shape. %H A270069 Alois P. Heinz, <a href="/A270069/b270069.txt">Table of n, a(n) for n = 0..200</a> %H A270069 Wikipedia, <a href="https://en.wikipedia.org/wiki/Tromino">Tromino</a> %Y A270069 Column k=9 of A270061. %K A270069 nonn %O A270069 0,2 %A A270069 _Alois P. Heinz_, Mar 09 2016