A047126 T(n,n+1), array T as in A047120.
1, 2, 6, 20, 71, 256, 938, 3480, 13041, 49234, 186968, 713428, 2733218, 10506788, 40506442, 156554820, 606400307, 2353368138, 9148789134, 35620615548, 138878821241, 542138013480, 2118718654794, 8288638523100, 32456517032946
Offset: 0