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 A278456 #10 Feb 06 2017 12:25:25 %S A278456 1,2,50,1954,56864,1532496,42238426,1178422563,32890293494, %T A278456 917103556607,25552076570350,711923354658732,19838824712825618, %U A278456 552851181380560869,15406086995815163663,429312063890812931103,11963383230714027535776,333377000620725693771782 %N A278456 Number of tilings of a 5 X n rectangle using pentominoes of any shape and monominoes. %H A278456 Alois P. Heinz, <a href="/A278456/b278456.txt">Table of n, a(n) for n = 0..692</a> %H A278456 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a> %e A278456 a(1) = 2: %e A278456 ._. ._. %e A278456 |_| | | %e A278456 |_| | | %e A278456 |_| | | %e A278456 |_| | | %e A278456 |_| |_| . %Y A278456 Column k=5 of A278657. %Y A278456 Cf. A174249, A233427, A273477. %K A278456 nonn %O A278456 0,2 %A A278456 _Alois P. Heinz_, Nov 22 2016