Number of defective (binary) heaps on 2n elements from the set {0,1} with exactly n defects.

Terms

a(0) =1a(1) =1a(2) =3a(3) =4a(4) =8a(5) =18a(6) =41a(7) =104a(8) =253a(9) =579a(10) =1370a(11) =3184a(12) =7331a(13) =16720a(14) =38720a(15) =91720a(16) =218038a(17) =518268a(18) =1259464a(19) =3141644a(20) =7687556a(21) =18460394a(22) =45409204a(23) =115174672a(24) =283748621a(25) =680088840a(26) =1665189408a(27) =4207220068a(28) =10403856572a(29) =25304979704