a(n) is the number of vertices formed by n-secting the angles of a nonagon (enneagon).

Terms

a(0) =9a(1) =19a(2) =135a(3) =118a(4) =396a(5) =379a(6) =135a(7) =712a(8) =1296a(9) =1243a(10) =1953a(11) =1891a(12) =2835a(13) =955a(14) =3708a(15) =3556a(16) =4806a(17) =4600a(18) =6003a(19) =5914a(20) =4860a(21) =7084a(22) =8838a(23) =8623a(24) =10395a(25) =10234a(26) =12339a(27) =7786a(28) =13941a(29) =13825