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 A247746 #6 Feb 06 2017 18:56:32
%S A247746 0,0,0,4,52,532,4772,44624,413332,3704668,32312456,277318708,
%T A247746 2365831332,20023322874,168065885292,1401084600204,11617827516556,
%U A247746 95910742322858,788559509624036,6459527069162538,52742304806108492,429408151732020490,3487057360672870112
%N A247746 Total number of Z shapes in all tilings of a 5 X n rectangle with pentominoes of any shape.
%H A247746 Alois P. Heinz, <a href="/A247746/b247746.txt">Table of n, a(n) for n = 0..500</a>
%H A247746 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a>
%F A247746 a(n) = Sum_{k>0} k * A247713(n,k).
%Y A247746 Cf. A174249, A233427, A247713.
%K A247746 nonn
%O A247746 0,4
%A A247746 _Alois P. Heinz_, Sep 23 2014