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 A247710 #13 Feb 06 2017 18:59:10 %S A247710 1,1,5,56,461,32,8,3558,368,80,23966,3256,696,24,8,178127,29564,6558, %T A247710 360,80,1362597,266672,61858,4852,770,24,8,10194184,2361632,581452, %U A247710 58732,8890,384,80,75684682,20056764,5220634,632044,97174,5968,914,24,8 %N A247710 Number T(n,k) of tilings of a 5 X n rectangle with pentominoes of any shape and exactly k pentominoes of shape W; triangle T(n,k), n>=0, 0<=k<=max(0,floor((n-2)/2)*2) read by rows. %C A247710 Sum_{k>0} k * T(n,k) = A247743(n). %H A247710 Alois P. Heinz, <a href="/A247710/b247710.txt">Rows n = 0..145, flattened</a> %H A247710 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a> %e A247710 T(4,2) = 8: %e A247710 ._______. ._______. ._______. %e A247710 | ._____| |_. |_. | | ._____| %e A247710 |_| ._| | | |_. | | |_| ._| | %e A247710 | ._| ._| | | |_| | | ._| | | %e A247710 |_|___| | | |_. |_| |_| ._| | %e A247710 |_______| (*2) |___|___| (*2) |___|___| (*4) %e A247710 Triangle T(n,k) begins: %e A247710 00 : 1; %e A247710 01 : 1; %e A247710 02 : 5; %e A247710 03 : 56; %e A247710 04 : 461, 32, 8; %e A247710 05 : 3558, 368, 80; %e A247710 06 : 23966, 3256, 696, 24, 8; %e A247710 07 : 178127, 29564, 6558, 360, 80; %e A247710 08 : 1362597, 266672, 61858, 4852, 770, 24, 8; %e A247710 09 : 10194184, 2361632, 581452, 58732, 8890, 384, 80; %e A247710 10 : 75684682, 20056764, 5220634, 632044, 97174, 5968, 914, 24, 8; %Y A247710 Row sums give A174249 or A233427(n,5). %Y A247710 Column k=0 gives A247774. %Y A247710 Cf. A247743. %K A247710 nonn,tabf %O A247710 0,3 %A A247710 _Alois P. Heinz_, Sep 23 2014