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 A372221 #18 May 07 2024 08:44:51 %S A372221 1,1,1,1,1,2,3,6,9,12,16,21,41,66,106,156,219,364,558,930,1444,2191, %T A372221 3515,5361,8737,13661,21478,34397,53528,86137,135294,215432,345081, %U A372221 546705,879212,1395476,2239086,3596427,5767656,9312008,14949738,24163742,39045229 %N A372221 Number of tilings of a 5 X n rectangle using n pentominoes of shapes T, W, I, X. %H A372221 Alois P. Heinz, <a href="/A372221/b372221.txt">Table of n, a(n) for n = 0..4472</a> %H A372221 Alois P. Heinz, <a href="/A372221/a372221.txt">G.f. for A372221</a> %H A372221 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a> %H A372221 <a href="/index/Rec#order_139">Index entries for linear recurrences with constant coefficients</a>, order 139. %e A372221 a(7) = 6: %e A372221 ._____________. ._____________. ._____________. %e A372221 | |_________| | | | | | | | | | |_________| | | %e A372221 | .___| |___. | | | | | | | | | |_________| | | %e A372221 |_| ._| |_. |_| | | | | | | | | |_________| | | %e A372221 | ._|_____|_. | | | | | | | | | |_________| | | %e A372221 |_|_________|_| |_|_|_|_|_|_|_| |_________|_|_| %e A372221 ._____________. ._____________. ._____________. %e A372221 | |_________| | | |_________| | | | |_________| %e A372221 |_. |_. ._| ._| | |_________| | | | |_________| %e A372221 | |___| |___| | | |_________| | | | |_________| %e A372221 | .___|_|___. | | |_________| | | | |_________| %e A372221 |_|_________|_| |_|_________|_| |_|_|_________| . %Y A372221 Cf. A003520, A174249, A366324. %K A372221 nonn,easy %O A372221 0,6 %A A372221 _Alois P. Heinz_, Apr 22 2024