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 A286391 #10 May 08 2017 11:45:09 %S A286391 1,1,15,344,6835,119392,2136080,38329669,688355077,12374676591, %T A286391 222673114420,4005005917279,72004800735036,1294444641691072, %U A286391 23273376392535695,418470613768822683,7524342117053834729,135288703461639048592,2432489164334993344213 %N A286391 Number of tilings of a 6 X n rectangle using pentominoes of shapes X, Y, Z, T and monominoes. %H A286391 Alois P. Heinz, <a href="/A286391/b286391.txt">Table of n, a(n) for n = 0..800</a> %H A286391 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a> %e A286391 a(2) = 15: %e A286391 .___. .___. .___. .___. .___. .___. .___. .___. .___. %e A286391 |_|_| | |_| |_| | | |_| |_|_| |_|_| |_|_| |_|_| | |_| %e A286391 |_|_| | ._| |_. | | ._| | |_| |_|_| |_|_| | |_| | |_| %e A286391 |_|_| | | | | | | | |_| | ._| | |_| | |_| | |_| | ._| %e A286391 |_|_| |_| | | |_| |_|_| | |_| | ._| | |_| | ._| |_|_| %e A286391 |_|_| |_. | | ._| |_|_| |_|_| | |_| | ._| |_|_| |_|_| %e A286391 |_|_| |_|_| |_|_| |_|_| |_|_| |_|_| |_|_| |_|_| |_|_| %e A286391 .___. .___. .___. .___. .___. .___. %e A286391 |_| | |_|_| |_|_| |_|_| |_|_| |_| | %e A286391 |_. | |_| | |_|_| |_|_| |_| | |_| | %e A286391 |_| | |_. | |_| | |_| | |_| | |_. | %e A286391 |_|_| |_| | |_. | |_| | |_. | |_|_| %e A286391 |_|_| |_|_| |_| | |_. | |_|_| |_|_| %e A286391 |_|_| |_|_| |_|_| |_|_| |_|_| |_|_| . %Y A286391 Cf. A247125, A278330, A278456, A278657, A278877, A278964, A286347. %K A286391 nonn %O A286391 0,3 %A A286391 _Alois P. Heinz_, May 08 2017