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 A247711 #17 May 09 2018 10:00:13 %S A247711 1,1,5,55,1,493,8,3930,76,27207,734,9,207118,7414,157,1622723,71986, %T A247711 2064,8,12544364,638499,22232,259,95912510,5558790,222964,3898,50, %U A247711 732066083,47971603,2179607,49537,948,8,5616480627,410502410,20604626,564498,13889,180 %N A247711 Number T(n,k) of tilings of a 5 X n rectangle with pentominoes of any shape and exactly k pentominoes of shape X; triangle T(n,k), n>=0, read by rows. %C A247711 Sum_{k>0} k * T(n,k) = A247744(n). %H A247711 Alois P. Heinz, <a href="/A247711/b247711.txt">Rows n = 0..185, flattened</a> %H A247711 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a> %e A247711 T(3,1) = 1: %e A247711 ._____. %e A247711 | ._. | %e A247711 |_| |_| %e A247711 |_. ._| %e A247711 | |_| | %e A247711 |_____| %e A247711 . %e A247711 Triangle T(n,k) begins: %e A247711 00 : 1; %e A247711 01 : 1; %e A247711 02 : 5; %e A247711 03 : 55, 1; %e A247711 04 : 493, 8; %e A247711 05 : 3930, 76; %e A247711 06 : 27207, 734, 9; %e A247711 07 : 207118, 7414, 157; %e A247711 08 : 1622723, 71986, 2064, 8; %e A247711 09 : 12544364, 638499, 22232, 259; %e A247711 10 : 95912510, 5558790, 222964, 3898, 50; %Y A247711 Row sums give A174249 or A233427(n,5). %Y A247711 Columns k=0-1 give: A247775, A247828. %Y A247711 Cf. A247744. %K A247711 nonn,tabf %O A247711 0,3 %A A247711 _Alois P. Heinz_, Sep 23 2014