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 A247705 #15 Feb 07 2017 10:15:32 %S A247705 1,1,5,48,8,423,68,10,3082,832,84,8,18998,7624,1230,88,10,133083, %T A247705 65360,14390,1732,116,8,965175,555236,150876,23184,2196,108,6,6907447, %U A247705 4531744,1454292,275320,33807,2616,124,4,48357538,36466396,13354738,3012116,457360,46872,3086,104,2 %N A247705 Number T(n,k) of tilings of a 5 X n rectangle with pentominoes of any shape and exactly k pentominoes of shape N; triangle T(n,k), n>=0, read by rows. %C A247705 Sum_{k>0} k * T(n,k) = A247738(n). %H A247705 Alois P. Heinz, <a href="/A247705/b247705.txt">Rows n = 0..160, flattened</a> %H A247705 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a> %e A247705 T(3,1) = 8: %e A247705 ._____. .___._. %e A247705 | ._. | | ._| | %e A247705 |_| |_| | | ._| %e A247705 | ._| | | | | | %e A247705 | | | |_|_| | %e A247705 |_|___| (*4) |_____| (*4) . %e A247705 Triangle T(n,k) begins: %e A247705 00 : 1; %e A247705 01 : 1; %e A247705 02 : 5; %e A247705 03 : 48, 8; %e A247705 04 : 423, 68, 10; %e A247705 05 : 3082, 832, 84, 8; %e A247705 06 : 18998, 7624, 1230, 88, 10; %e A247705 07 : 133083, 65360, 14390, 1732, 116, 8; %e A247705 08 : 965175, 555236, 150876, 23184, 2196, 108, 6; %Y A247705 Row sums give A174249 or A233427(n,5). %Y A247705 Column k=0 gives A247769. %Y A247705 Cf. A247738. %K A247705 nonn,tabf %O A247705 0,3 %A A247705 _Alois P. Heinz_, Sep 22 2014