a(n) is the number of noncomposites (primes or 1) that are n digits long in balanced ternary notation.

A233919

a(n) is the number of noncomposites (primes or 1) that are n digits long in balanced ternary notation.

Terms

    a(0) =1a(1) =2a(2) =4a(3) =6a(4) =18a(5) =42a(6) =111a(7) =279a(8) =752a(9) =1990a(10) =5376a(11) =14707a(12) =40465a(13) =111970a(14) =311997a(15) =873239a(16) =2455818a(17) =6933060a(18) =19640273a(19) =55813426a(20) =159047591a(21) =454373344a(22) =1301016216a(23) =3733009232a(24) =10731465131a(25) =30904208376a(26) =89140202911a(27) =257498974953a(28) =744861243809

External references