257500

Appears in sequences

• a(0)=1, a(1)=2, a(n) = a(n-1)*9/2 - Catalan(n-1) where Catalan(n) = binomial(2n,n)/(n+1) = A000108(n).at n=9A067336
• Square array read by antidiagonals: T(n,k)=T(n,k-1)*n^2/(n-1)-Catalan(k-1) with a(n,1)=n-1 and a(1,k)=0 where Catalan(k)=C(2k,k)/(k+1)=A000108(k).at n=57A067346