Number of compositions (ordered partitions) of n with designated summands.

Terms

a(0) =1a(1) =1a(2) =3a(3) =6a(4) =14a(5) =30a(6) =69a(7) =153a(8) =345a(9) =771a(10) =1730a(11) =3873a(12) =8682a(13) =19450a(14) =43590a(15) =97668a(16) =218864a(17) =490416a(18) =1098933a(19) =2462458a(20) =5517870a(21) =12364356a(22) =27705944a(23) =62083134a(24) =139115247a(25) =311727845a(26) =698516370a(27) =1565227653a(28) =3507344882a(29) =7859219406