398684

Appears in sequences

• Number of nonempty subsets of {1,2,...,n} in which exactly 4/5 of the elements are <= (n+2)/3.at n=36A048079
• Number of nonempty subsets of {1,2,...,n} in which exactly 4/5 of the elements are <= (n+3)/3.at n=36A048090
• a(n) = C(n)*(9*n + 1) where C(n) = Catalan numbers (A000108).at n=9A050479
• a(0) = 0; a(n) = C(2*n-2,n-1)*(n^2-2*n+2)/n for n >= 1.at n=10A180266