Number of compositions of n having exactly three fixed points.

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =12a(5) =30a(6) =61a(7) =126a(8) =258a(9) =537a(10) =1083a(11) =2205a(12) =4465a(13) =9023a(14) =18192a(15) =36612a(16) =73633a(17) =147893a(18) =296818a(19) =595313a(20) =1193351a(21) =2391121a(22) =4789448a(23) =9590503a(24) =19199906a(25) =38430421a(26) =76910470a(27) =153901337a(28) =307932963a(29) =616076971