Number of 2n-length strings of balanced parentheses of exactly 4 different types that are introduced in ascending order.

A258392

Number of 2n-length strings of balanced parentheses of exactly 4 different types that are introduced in ascending order.

Terms

    a(0) =14a(1) =420a(2) =8580a(3) =150150a(4) =2432430a(5) =37777740a(6) =572827580a(7) =8568059500a(8) =127199546012

External references