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 A247828 #8 Feb 06 2017 18:38:52 %S A247828 0,0,0,1,8,76,734,7414,71986,638499,5558790,47971603,410502410, %T A247828 3473846885,29078659564,241699322196,1997778940804,16429720592636, %U A247828 134489816829048,1096404231410945,8906880161717904,72131791267258552,582512418898356698,4692186192041626600 %N A247828 Number of tilings of a 5 X n rectangle using n pentominoes of any shape including exactly one X shape. %H A247828 Alois P. Heinz, <a href="/A247828/b247828.txt">Table of n, a(n) for n = 0..500</a> %H A247828 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a> %e A247828 a(3) = 1: %e A247828 ._____. %e A247828 | ._. | %e A247828 |_| |_| %e A247828 |_. ._| %e A247828 | |_| | %e A247828 |_____| . %Y A247828 Column k=1 of A247711. %K A247828 nonn %O A247828 0,5 %A A247828 _Alois P. Heinz_, Sep 24 2014