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 A247742 #6 Feb 06 2017 19:01:13
%S A247742 0,0,0,20,192,1568,12636,114216,1022604,8640980,72406668,605996308,
%T A247742 5065065936,42045917448,346705312932,2848191025876,23325323646860,
%U A247742 190440300054560,1550193295412264,12585187313440032,101937894879304356,823951520087842720,6646993031822674592
%N A247742 Total number of V shapes in all tilings of a 5 X n rectangle with pentominoes of any shape.
%H A247742 Alois P. Heinz, <a href="/A247742/b247742.txt">Table of n, a(n) for n = 0..500</a>
%H A247742 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a>
%F A247742 a(n) = Sum_{k>0} k * A247709(n,k).
%Y A247742 Cf. A174249, A233427, A247709.
%K A247742 nonn
%O A247742 0,4
%A A247742 _Alois P. Heinz_, Sep 23 2014