T(2n,n-4), T given by A026780.

Terms

a(0) =1a(1) =19a(2) =220a(3) =2021a(4) =16246a(5) =119914a(6) =835080a(7) =5579147a(8) =36150820a(9) =228879616a(10) =1423367610a(11) =8727874180a(12) =52919787978a(13) =317969615146