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 A234931 #14 Feb 06 2017 17:45:58 %S A234931 1,0,0,0,2,0,0,0,4,0,8,0,16,0,40,0,64,16,200,96,504,464,1528,1664, %T A234931 4376,5616,12792,18192,38264,58384,115832,186368,355808,589344, %U A234931 1095408,1853664,3383656,5802016,10470376,18125280,32461312,56552736,100782696,176318464 %N A234931 Number of tilings of a 5 X n rectangle using n pentominoes of shapes F, U, N. %H A234931 Alois P. Heinz, <a href="/A234931/b234931.txt">Table of n, a(n) for n = 0..1000</a> %H A234931 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a> %F A234931 G.f.: (4*x^20 +4*x^18 +8*x^16 -3*x^14 +4*x^13 -5*x^12 -2*x^11 +3*x^10 -2*x^9 +6*x^8 -2*x^7 +2*x^6 -2*x^5 -x^4 +2*x -1) / (-8*x^22 -28*x^20 -6*x^18 +8*x^17 +26*x^16 +4*x^15 +7*x^14 -8*x^13 -9*x^12 -14*x^11 +7*x^10 +2*x^9 +8*x^8 -2*x^7 +2*x^6 -6*x^5 +x^4 +2*x -1). %e A234931 a(4) = 2: %e A234931 ._______. ._______. %e A234931 | | ._. | | ._. | | %e A234931 | |_| |_| |_| |_| | %e A234931 |_. |_. | | ._| ._| %e A234931 | |_| | | | | |_| | %e A234931 |_____|_| |_|_____|. %Y A234931 Cf. A174249, A233427, A234312, A247680, A247126. %K A234931 nonn %O A234931 0,5 %A A234931 _Alois P. Heinz_, Jan 01 2014