Number of stars of visual magnitude n.

Terms

a(0) =2a(1) =6a(2) =14a(3) =71a(4) =190a(5) =610a(6) =1929a(7) =5946a(8) =17765a(9) =51094a(10) =140062a(11) =409194a(12) =1196690a(13) =3481113a(14) =10126390a(15) =29457184a(16) =85689537a(17) =249266759a(18) =725105060a(19) =2109295881a(20) =6135840666a(21) =17848866544