%I #8 Mar 14 2021 00:47:05
%S 1,3,16,132,2016,44928,1551744,68542848,4211122176,309852407808,
%T 29839376553984,3304540891072512,460231661327007744,
%U 71669823905083834368,13644939814369185890304,2845529932444144841981952,710399582113730769218174976,191237460565395319832268767232
%N Number of perfect matchings in the 4 X n rook graph.
%H Andrew Howroyd, <a href="/A341852/b341852.txt">Table of n, a(n) for n = 0..50</a>
%Y Row n=4 of A341850.
%K nonn
%O 0,2
%A _Andrew Howroyd_, Feb 21 2021