The number of bidirectional ballot sequences of length n, i.e., the number of 0-1 sequences of length n such that every prefix and every suffix has more 1's than 0's.
A167510
The number of bidirectional ballot sequences of length n, i.e., the number of 0-1 sequences of length n such that every prefix and every suffix has more 1's than 0's.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =3a(6) =5a(7) =9a(8) =15a(9) =28a(10) =49a(11) =91a(12) =166a(13) =307a(14) =574a(15) =1065a(16) =2016a(17) =3769a(18) =7176a(19) =13532a(20) =25842a(21) =49113a(22) =93995a(23) =179775a(24) =344796a(25) =662676a(26) =1273880a(27) =2457275a(28) =4735080a(29) =9158972
External references
- oeis: A167510