Number of distinct languages accepted by unary DFA's with n states.

Terms

a(0) =2a(1) =6a(2) =18a(3) =48a(4) =126a(5) =306a(6) =738a(7) =1716a(8) =3936a(9) =8862a(10) =19770a(11) =43560a(12) =95310a(13) =206874a(14) =446478a(15) =958236a(16) =2047542a(17) =4356660a(18) =9237606a(19) =19522752a(20) =41142522a(21) =86477298a(22) =181343202a(23) =379459284a(24) =792472968a(25) =1652046606a(26) =3438310428a(27) =7145039916a(28) =14826950742