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 A247713 #12 Feb 06 2017 18:56:06 %S A247713 1,1,5,52,4,451,48,2,3498,484,24,23502,4136,300,12,173611,37674,3262, %T A247713 142,1323447,335388,35938,1964,44,9920654,2892492,365458,25752,986,12, %U A247713 73573634,24266128,3544842,298200,15002,400,6,545170514,200531918,33123244,3236018,198380,7546,164,2 %N A247713 Number T(n,k) of tilings of a 5 X n rectangle with pentominoes of any shape and exactly k pentominoes of shape Z; triangle T(n,k), n>=0, read by rows. %C A247713 Sum_{k>0} k * T(n,k) = A247746(n). %H A247713 Alois P. Heinz, <a href="/A247713/b247713.txt">Rows n = 0..170, flattened</a> %H A247713 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a> %e A247713 T(3,1) = 4: %e A247713 ._____. ._____. %e A247713 |___. | | ._| %e A247713 |_. | | |___| | %e A247713 | | |_| | .___| %e A247713 | |___| |_| | %e A247713 |_____| (*2) |_____| (*2) . %e A247713 Triangle T(n,k) begins: %e A247713 00 : 1; %e A247713 01 : 1; %e A247713 02 : 5; %e A247713 03 : 52, 4; %e A247713 04 : 451, 48, 2; %e A247713 05 : 3498, 484, 24; %e A247713 06 : 23502, 4136, 300, 12; %e A247713 07 : 173611, 37674, 3262, 142; %e A247713 08 : 1323447, 335388, 35938, 1964, 44; %e A247713 09 : 9920654, 2892492, 365458, 25752, 986, 12; %e A247713 10 : 73573634, 24266128, 3544842, 298200, 15002, 400, 6; %Y A247713 Row sums give A174249 or A233427(n,5). %Y A247713 Column k=0 gives A247777. %Y A247713 Cf. A247746. %K A247713 nonn,tabf %O A247713 0,3 %A A247713 _Alois P. Heinz_, Sep 23 2014