18696432domain: NAppears in sequencesa(n) = 2^(2*n+1) - C(2*n+3,n+1) + C(2*n+1,n).at n=12A006419Number of valleys at level 0 in all dispersed Dyck paths of length n (i.e., in all Motzkin paths of length n with no (1,0) steps at positive heights).at n=26A191389a(n) = Sum_{k=0..11} C(n, k).at n=26A219531