a(n) = Sum_{k=0..n} A000108(k) * A000041(k).

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =91a(5) =385a(6) =1837a(7) =8272a(8) =39732a(9) =185592a(10) =891024a(11) =4183040a(12) =20199964a(13) =95232864a(14) =456282264a(15) =2162574984a(16) =10330196754a(17) =48834699384a(18) =232725598884