Number of compositions of n having exactly two fixed points.

Terms

a(0) =1a(1) =1a(2) =3a(3) =4a(4) =12a(5) =23a(6) =47a(7) =100a(8) =198a(9) =404a(10) =818a(11) =1652a(12) =3319a(13) =6686a(14) =13426a(15) =26947a(16) =54043a(17) =108331a(18) =217059a(19) =434731a(20) =870472a(21) =1742558a(22) =3487710a(23) =6979593a(24) =13965902a(25) =27942597a(26) =55902624a(27) =111833288a(28) =223711791a(29) =447496476