Third diagonal of A027537.

Terms

a(0) =19a(1) =319a(2) =2816a(3) =18254a(4) =99093a(5) =481821a(6) =2182330a(7) =9438700a(8) =39629855a(9) =163365899a(10) =666397044a(11) =2704448010a(12) =10958782249a(13) =44439844153a(14) =180582177902a(15) =735754592168