a(n)=T(n,n+3), array T as in A049600.

Terms

a(0) =0a(1) =1a(2) =7a(3) =43a(4) =253a(5) =1462a(6) =8378a(7) =47818a(8) =272422a(9) =1550927a(10) =8829033a(11) =50276013a(12) =286430763a(13) =1632808572a(14) =9313861092a(15) =53163187748a(16) =303653552188