1441999

Appears in sequences

• Number of equivalence classes of ballot paths of length n for the string ddu.at n=40A274112
• Number of equivalence classes of Dyck paths of semilength n for the string duu.at n=21A274115
• a(n) = Sum_{k=0..n} (4*k+1) * binomial(2*n+2*k+1,n-k)/(2*n+2*k+1).at n=10A390527