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 A247739 #6 Feb 06 2017 18:35:50
%S A247739 0,0,4,60,556,5328,45316,405636,3583136,30801264,261702184,2204389124,
%T A247739 18485952896,154072120428,1276431617512,10525735832272,86463238965520,
%U A247739 707822586795020,5776135319900600,47001025464956044,381480686633266156,3089168335328298424,24963223479997963992
%N A247739 Total number of P shapes in all tilings of a 5 X n rectangle with pentominoes of any shape.
%H A247739 Alois P. Heinz, <a href="/A247739/b247739.txt">Table of n, a(n) for n = 0..500</a>
%H A247739 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a>
%F A247739 a(n) = Sum_{k>0} k * A247706(n,k).
%Y A247739 Cf. A174249, A233427, A247706.
%K A247739 nonn
%O A247739 0,3
%A A247739 _Alois P. Heinz_, Sep 23 2014