a(n) = floor(tan(m*Pi/2)), where m = 1 - 1/n.

Terms

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