Follow n+1 by n. Also (essentially) Molien series of 2-dimensional quaternion group Q_8.

Terms

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