18792303domain: NAppears in sequencesa(n) = T(n,n), T given by A026568. Also a(n) = number of integer strings s(0),...,s(n) counted by T, such that s(n)=0.at n=20A026569a(n) = Sum_{k=0..n} binomial(2*k,k)*binomial(2*n-k,k).at n=10A027277