Number of compositions of n with exactly two descents.

Terms

a(0) =2a(1) =8a(2) =29a(3) =81a(4) =205a(5) =469a(6) =1013a(7) =2059a(8) =4021a(9) =7558a(10) =13780a(11) =24440a(12) =42358a(13) =71867a(14) =119715a(15) =196084a(16) =316362a(17) =503410a(18) =791043a(19) =1228636a(20) =1888003a(21) =2872541a(22) =4330299a(23) =6471778a(24) =9594556a(25) =14116745a(26) =20622825a(27) =29925512a(28) =43149302a(29) =61843197