A026092 a(n) = T(2n,n-1), where T is the array defined in A026082.
1, 1, 9, 45, 248, 1377, 7756, 44096, 252570, 1455166, 8424011, 48960606, 285512823, 1669721225, 9788890230, 57511916805, 338536358979, 1996103321754, 11787262391390, 69699393574522
Offset: 1