196947587823domain: NAppears in sequencesa(n) = binomial(3*n+1,n)/(n+1).at n=16A006013If n = 2*m then a(n) = binomial(3*m, m)/(2*m+1), if n=2*m+1 then a(n) = binomial(3*m+1, m+1)/(2*m+1).at n=33A047749Number of primitive (1,1) pairs in the Fibonacci tree at depth 3n.at n=16A305574