a(n) = [x^prime(n)] Product_{k=1..n} (x^prime(k) + 1 + 1/x^prime(k)).

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =6a(5) =13a(6) =31a(7) =77a(8) =188a(9) =449a(10) =1191a(11) =3014a(12) =7920a(13) =21498a(14) =57833a(15) =154073a(16) =412733a(17) =1141274a(18) =3106771a(19) =8576977a(20) =24015471a(21) =66489615a(22) =185886699a(23) =517837152a(24) =1435964205a(25) =4034697191a(26) =11438332340a(27) =32395341851a(28) =92396549863a(29) =263233759500