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 A247125 #19 Feb 06 2017 18:40:08 %S A247125 1,0,2,1,16,10,59,60,330,397,1520,2218,7875,12820,39250,70045,202168, %T A247125 384866,1038051,2073580,5385754,11156701,28015232,59580154,146333795, %U A247125 317517636,766142242,1686735709,4019319048,8946988370,21116854115,47386013020,111065223914 %N A247125 Number of tilings of a 5 X n rectangle using n pentominoes of shapes L, U, X. %H A247125 Alois P. Heinz, <a href="/A247125/b247125.txt">Table of n, a(n) for n = 0..1000</a> %H A247125 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a> %H A247125 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0,2,1,12,6,2). %F A247125 G.f.: -1/(2*x^6+6*x^5+12*x^4+x^3+2*x^2-1). %e A247125 a(4) = 16: %e A247125 ._______. ._______. ._______. %e A247125 | ._____| | ._____| | ._| ._| %e A247125 |_| |_. | |_| |_. | | | | | | %e A247125 |_. ._| | |_. ._| | | | | | | %e A247125 | |_|___| | |_| | | |_| |_| | %e A247125 |_______| (2) |_____|_| (4) |___|___| (4) %e A247125 ._______. ._______. %e A247125 | ._____| | ._____| %e A247125 |_| ._. | |_|_. | | %e A247125 | |_| |_| | ._| | | %e A247125 |_____| | | |___| | %e A247125 |_______| (2) |___|___| (4) . %p A247125 a:= n-> (<<0|1|0|0|0|0>, <0|0|1|0|0|0>, <0|0|0|1|0|0>, %p A247125 <0|0|0|0|1|0>, <0|0|0|0|0|1>, <2|6|12|1|2|0>>^n)[6,6]: %p A247125 seq(a(n), n=0..40); %Y A247125 Cf. A174249, A233427, A234312, A247124, A247268. %K A247125 nonn %O A247125 0,3 %A A247125 _Alois P. Heinz_, Nov 19 2014