a(3n) = a(3n-1) + a(3n-2), a(3n+1) = 2n*a(3n) + a(3n-1), a(3n+2) = a(3n+1) + a(3n).

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =8a(5) =11a(6) =19a(7) =87a(8) =106a(9) =193a(10) =1264a(11) =1457a(12) =2721a(13) =23225a(14) =25946a(15) =49171a(16) =517656a(17) =566827a(18) =1084483a(19) =13580623a(20) =14665106a(21) =28245729a(22) =410105312a(23) =438351041a(24) =848456353a(25) =14013652689a(26) =14862109042a(27) =28875761731a(28) =534625820200