A006983(n) + 1.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =1a(8) =1a(9) =1a(10) =1a(11) =1a(12) =1a(13) =1a(14) =1a(15) =1a(16) =1a(17) =1a(18) =1a(19) =1a(20) =2a(21) =9a(22) =13a(23) =27a(24) =161a(25) =442a(26) =1153a(27) =3002a(28) =7902