The Poincar\'e series for the algebras of joint invariants and covariants of $n$ linear forms

Explicit formulas for computation of the Poincar'e series for the algebras of joint $S{L}_2$-invariants and covariants of $n$ linear forms in terms of Narayana polynomials are found. Also, for these algebras we calculate the degrees and asymptotic behavious of the degrees.