A026863 T(2n,n+3), T given by A026747.
1, 9, 56, 301, 1504, 7217, 33821, 156274, 716116, 3266558, 14868789, 67649170, 307997855, 1404343584, 6416130302, 29383457373, 134915391509, 621163581667, 2867888163907, 13278007815855, 61645847283931, 286977785803129
Offset: 3