a(n) = C(n) + 1 - 0^n where C(n) = A000108(n).

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =15a(5) =43a(6) =133a(7) =430a(8) =1431a(9) =4863a(10) =16797a(11) =58787a(12) =208013a(13) =742901a(14) =2674441a(15) =9694846a(16) =35357671a(17) =129644791a(18) =477638701a(19) =1767263191a(20) =6564120421a(21) =24466267021a(22) =91482563641a(23) =343059613651