Number of (binary) max-heaps on 2n elements from the set {0,1} containing n 0's and n 1's.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =7a(5) =13a(6) =27a(7) =54a(8) =109a(9) =219a(10) =460a(11) =962a(12) =1986a(13) =4044a(14) =8516a(15) =18058a(16) =37801a(17) =77701a(18) =164300a(19) =350336a(20) =738945a(21) =1530521a(22) =3250659a(23) =6962248a(24) =14735660a(25) =30625898a(26) =65206770a(27) =140040538a(28) =297712980a(29) =622136512