%I
%S 22,9482,112269228,37515056726494,355023905438833546724
%N Number of paths joining opposite corners of an n X n grid with every vertex appearing at most twice in the path.
%e The 22 paths in a 2 X 2 grid whose nodes are numbered from 1 to 4 in the natural way are 124, 134, 12124, 12134, 12424, 12434, 13124, 13134, 13424, 13434, 1212434, 1213424, 1213434, 1242134, 1243124, 1243134, 1312424, 1312434, 1313424, 1342124, 1342134, 1343124.  _Giovanni Resta_, Mar 24 2014
%Y Cf. A007764, A239688.
%K nonn,more
%O 2,1
%A _Muhammad Kholilurrohman_, Jan 09 2014
%E a(5)a(6) from _Muhammad Kholilurrohman_, Nov 13 2014
