Expansion of g.f. (1-x-x^2)/(1-x-3*x^2-x^3).

Terms

a(0) =1a(1) =0a(2) =2a(3) =3a(4) =9a(5) =20a(6) =50a(7) =119a(8) =289a(9) =696a(10) =1682a(11) =4059a(12) =9801a(13) =23660a(14) =57122a(15) =137903a(16) =332929a(17) =803760a(18) =1940450a(19) =4684659a(20) =11309769a(21) =27304196a(22) =65918162a(23) =159140519a(24) =384199201a(25) =927538920a(26) =2239277042a(27) =5406093003a(28) =13051463049a(29) =31509019100