a(n) = A000009(A000009(n)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =2a(7) =3a(8) =4a(9) =6a(10) =10a(11) =15a(12) =27a(13) =46a(14) =89a(15) =192a(16) =390a(17) =864a(18) =2304a(19) =5718a(20) =16444a(21) =53250a(22) =173682a(23) =618784a(24) =2556284a(25) =11086968a(26) =53466624a(27) =299016608a(28) =1780751883a(29) =11784471548