a(0) = 0, a(1) = 1, a(2) = 1; thereafter a(n) = 5*a(n-1) - 4*a(n-2) + a(n-3).

Terms

a(0) =0a(1) =1a(2) =1a(3) =1a(4) =2a(5) =7a(6) =28a(7) =114a(8) =465a(9) =1897a(10) =7739a(11) =31572a(12) =128801a(13) =525456a(14) =2143648a(15) =8745217a(16) =35676949a(17) =145547525a(18) =593775046a(19) =2422362079a(20) =9882257736a(21) =40315615410a(22) =164471408185a(23) =670976837021