The number of binary heaps on n elements whose breadth-first search reading word avoids 231.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =7a(6) =14a(7) =37a(8) =80a(9) =222a(10) =544a(11) =1601a(12) =4095a(13) =12416a(14) =33785a(15) =105769a(16) =293747a(17) =935184a(18) =2717376a(19) =8848014a(20) =26134254a(21) =86210716a(22) =262068267a(23) =877833206a(24) =2695238060a(25) =9109101156a(26) =28619396967a(27) =97879220771a(28) =310021153392