10318939956domain: NAppears in sequencesa(0)=1, for n>=1 a(n) = Sum_{k=0..n} 5^k*N(n,k) where N(n,k) = C(n,k)*C(n,k+1)/n are the Narayana numbers (A001263).at n=12A078009Series reversion of x/(1+6x+5x^2).at n=12A127848