a(n) = A359720(3*n+1,2*n) for n >= 0.

Terms

a(0) =1a(1) =9a(2) =54a(3) =269a(4) =1254a(5) =5642a(6) =24828a(7) =107613a(8) =461318a(9) =1961102a(10) =8282196a(11) =34792914a(12) =145527004a(13) =606473844a(14) =2519619640a(15) =10440010845a(16) =43158028230a(17) =178049440230a(18) =733229991780