%I #19 Jan 30 2022 12:31:25
%S 1,2,104,111712,2688307514,1445778936756068,17337631013706758184626,
%T 4628650743368437273677525554148,
%U 27478778338807945303765092195103685118924
%N Number of simple Hamiltonian paths connecting opposite corners of a 2n+1 X 2n+1 grid.
%F a(n) = A121788(2n), n>0. - _Ashutosh Mehra_, Dec 19 2008
%Y Cf. A121788, A333580.
%K nonn,more,walk
%O 0,2
%A _Don Knuth_, Dec 07 1995
%E a(7)-a(8) copied from A121788 by _Alois P. Heinz_, Sep 27 2014