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A243647 Number of ways four L-tiles can be placed on an n X n square.

%I A243647 #7 Jun 08 2014 12:49:42
%S A243647 0,0,0,0,1,176,3145,22969,106819,376796,1101151,2805825,6438909,
%T A243647 13602304,26866541,50186401,89436655,153088924,253052339,405702361,
%U A243647 633123801,964595760,1438347889,2103619049,3023051131,4275452476,5958967015,8194686929,11130748309
%N A243647 Number of ways four L-tiles can be placed on an n X n square.
%H A243647 Alois P. Heinz, <a href="/A243647/b243647.txt">Table of n, a(n) for n = 0..1000</a>
%F A243647 G.f.: -x^4*(9*x^8 -102*x^7 +253*x^6 +179*x^5 -1340*x^4 +916*x^3 +1597*x^2 +167*x+1) / (x-1)^9.
%F A243647 a(n) = (n^8 -8*n^7 -14*n^6 +244*n^5 -201*n^4 -2428*n^3 +4042*n^2 +7700*n -15576) / 24 for n>=4, a(n) = 0 for n<4.
%e A243647 a(4) = 1:
%e A243647 ._______.
%e A243647 | |_| |_|
%e A243647 |___|___|
%e A243647 | |_| |_|
%e A243647 |___|___| .
%p A243647 a:= n-> `if`(n<4, 0, ((((((((n-8)*n-14)*n+244)*n-201)*n
%p A243647          -2428)*n+4042)*n+7700)*n-15576)/24):
%p A243647 seq(a(n), n=0..50);
%Y A243647 Column k=4 of A243608.
%K A243647 nonn,easy
%O A243647 0,6
%A A243647 _Alois P. Heinz_, Jun 08 2014