Number of ternary irreducible monic polynomials of degree n; dimensions of free Lie algebras.

Terms

a(0) =1a(1) =3a(2) =3a(3) =8a(4) =18a(5) =48a(6) =116a(7) =312a(8) =810a(9) =2184a(10) =5880a(11) =16104a(12) =44220a(13) =122640a(14) =341484a(15) =956576a(16) =2690010a(17) =7596480a(18) =21522228a(19) =61171656a(20) =174336264a(21) =498111952a(22) =1426403748a(23) =4093181688a(24) =11767874940a(25) =33891544368a(26) =97764009000a(27) =282429535752a(28) =817028131140