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 A243217 #7 Jun 01 2014 14:42:41 %S A243217 0,0,0,0,3388,157000,2135356,15836664,81324796,325679904,1088989348, %T A243217 3174085648,8301786980,19888285976,44304931948,92833927816, %U A243217 184597383660,350812701616,640815379476,1130391980512,1933082192404,3215240556392,5215796556572,8271817286296 %N A243217 Number of 5-matchings of the n X n grid graph. %C A243217 Number of ways 5 dominoes can be placed on an n X n chessboard. %H A243217 Alois P. Heinz, <a href="/A243217/b243217.txt">Table of n, a(n) for n = 0..1000</a> %F A243217 G.f.: 4*(2*x^11 -6*x^10 +17*x^9 -559*x^8 +3298*x^7 -5840*x^6 -8668*x^5 +55222*x^4 -105932*x^3 -148674*x^2 -29933*x -847)*x^4 / (x-1)^11. %F A243217 a(n) = (4*n^10 -20*n^9 -100*n^8 +640*n^7 +635*n^6 -7589*n^5 +2370*n^4 +39275*n^3 -35789*n^2 -74246*n +86580)/15 for n>=5, a(4) = 3388, a(n) = 0 for n<=3. %p A243217 a:= n-> `if`(n<5, [0$4, 3388][n+1], ((((((((((4*n-20)*n-100)*n+640) %p A243217 *n+635)*n-7589)*n+2370)*n+39275)*n-35789)*n-74246)*n+86580)/15): %p A243217 seq(a(n), n=0..40); %Y A243217 Column k=5 of A242861. %K A243217 nonn %O A243217 0,5 %A A243217 _Alois P. Heinz_, Jun 01 2014