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 A278964 #12 May 08 2017 11:45:20 %S A278964 1,1,31,432,9851,150749,2392788,38885816,646657365,10599739324, %T A278964 173226495187,2835753730682,46501906844608,762113847626540, %U A278964 12484929995911672,204541850515528677,3351522453919340317,54915791725126323755,899777273419073185968 %N A278964 Number of tilings of a 6 X n rectangle using pentominoes of shapes L, U, X and monominoes. %H A278964 Alois P. Heinz, <a href="/A278964/b278964.txt">Table of n, a(n) for n = 0..824</a> %H A278964 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a> %e A278964 a(2) = 31: %e A278964 .___. .___. .___. .___. .___. .___. .___. .___. .___. .___. .___. %e A278964 |_|_| | ._| | ._| |_|_| |_|_| |_|_| |_. | |_. | |_|_| |_|_| |_|_| %e A278964 |_|_| | |_| | |_| | ._| |_|_| |_|_| |_| | |_| | |_. | |_|_| |_|_| %e A278964 |_|_| |___| |___| | |_| | ._| |_|_| |___| |___| |_| | |_. | |_|_| %e A278964 |_|_| | ._| |_|_| |___| | |_| | ._| |_. | |_|_| |___| |_| | |_. | %e A278964 |_|_| | |_| |_|_| |_|_| |___| | |_| |_| | |_|_| |_|_| |___| |_| | %e A278964 |_|_| |___| |_|_| |_|_| |_|_| |___| |___| |_|_| |_|_| |_|_| |___| %e A278964 .___. .___. .___. .___. .___. .___. .___. .___. .___. .___. .___. %e A278964 | ._| |_. | | |_| |_|_| |_|_| |_. | |_. | |_|_| |_. | |_|_| |_|_| %e A278964 | |_| |_| | | |_| | |_| |_|_| | | | |_| | |_. | |_| | |_. | |_|_| %e A278964 |___| |___| | |_| | |_| | |_| | | | | | | | | | |_| | |_| | |_. | %e A278964 |_. | | ._| |___| | |_| | |_| | |_| | |_| | | | |_|_| |_| | |_| | %e A278964 |_| | | |_| |_|_| |___| | |_| |___| | |_| | |_| |_|_| |_|_| |_| | %e A278964 |___| |___| |_|_| |_|_| |___| |_|_| |___| |___| |_|_| |_|_| |_|_| %e A278964 .___. .___. .___. .___. .___. .___. .___. .___. .___. %e A278964 | ._| |_|_| |_|_| | ._| | ._| |_|_| |_|_| |_|_| |_| | %e A278964 | |_| | ._| |_|_| | | | | |_| | ._| |_|_| |_| | |_| | %e A278964 | |_| | |_| | ._| | | | | | | | | | |_| | |_| | |_| | %e A278964 |_|_| | |_| | |_| |_| | |_| | | | | |_| | |_| | |___| %e A278964 |_|_| |_|_| | |_| |___| |_| | |_| | |_| | |___| |_|_| %e A278964 |_|_| |_|_| |_|_| |_|_| |___| |___| |___| |_|_| |_|_| . %Y A278964 Cf. A247125, A278330, A278456, A278657, A278877, A286391. %K A278964 nonn %O A278964 0,3 %A A278964 _Alois P. Heinz_, Dec 02 2016