Sectors around outside of dartboard.

Terms

a(0) =20a(1) =1a(2) =18a(3) =4a(4) =13a(5) =6a(6) =10a(7) =15a(8) =2a(9) =17a(10) =3a(11) =19a(12) =7a(13) =16a(14) =8a(15) =11a(16) =14a(17) =9a(18) =12a(19) =5a(20) =20a(21) =1a(22) =18a(23) =4a(24) =13a(25) =6a(26) =10a(27) =15a(28) =2a(29) =17