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 A247709 #14 Feb 06 2017 19:00:49 %S A247709 1,1,5,38,16,2,329,152,20,2614,1224,160,8,17400,8656,1714,168,12, %T A247709 122843,72104,17280,2300,158,4,901647,598444,168422,25872,2284,108,4, %U A247709 6662758,4770520,1479850,260672,29166,2256,124,8,48492622,37416964,12800398,2601524,351578,32840,2182,100,4 %N A247709 Number T(n,k) of tilings of a 5 X n rectangle with pentominoes of any shape and exactly k pentominoes of shape V; triangle T(n,k), n>=0, 0<=k<=max(0,n-2+delta_{n,3}), read by rows. %C A247709 Sum_{k>0} k * T(n,k) = A247742(n). %H A247709 Alois P. Heinz, <a href="/A247709/b247709.txt">Rows n = 0..145, flattened</a> %H A247709 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a> %e A247709 T(3,2) = 2: %e A247709 ._____. ._____. %e A247709 | .___| |___. | %e A247709 | | ._| |_. | | %e A247709 |_| | | | | |_| %e A247709 |___| | | |___| %e A247709 |_____| |_____| . %e A247709 Triangle T(n,k) begins: %e A247709 00 : 1; %e A247709 01 : 1; %e A247709 02 : 5; %e A247709 03 : 38, 16, 2; %e A247709 04 : 329, 152, 20; %e A247709 05 : 2614, 1224, 160, 8; %e A247709 06 : 17400, 8656, 1714, 168, 12; %e A247709 07 : 122843, 72104, 17280, 2300, 158, 4; %e A247709 08 : 901647, 598444, 168422, 25872, 2284, 108, 4; %e A247709 09 : 6662758, 4770520, 1479850, 260672, 29166, 2256, 124, 8; %e A247709 10 : 48492622, 37416964, 12800398, 2601524, 351578, 32840, 2182, 100, 4; %Y A247709 Row sums give A174249 or A233427(n,5). %Y A247709 Column k=0 gives A247773. %Y A247709 Cf. A247742. %K A247709 nonn,tabf %O A247709 0,3 %A A247709 _Alois P. Heinz_, Sep 22 2014