Number of distinct values taken by 4^4^...^4 (with n 4's and parentheses inserted in all possible ways).

A003019

Number of distinct values taken by 4^4^...^4 (with n 4's and parentheses inserted in all possible ways).

Terms

    a(0) =1a(1) =1a(2) =2a(3) =4a(4) =9a(5) =20a(6) =48a(7) =114a(8) =282a(9) =703a(10) =1787a(11) =4583a(12) =11900a(13) =31131a(14) =82117a(15) =217954a(16) =581970a(17) =1561704a(18) =4210263a(19) =11396488a(20) =30963024a(21) =84402984a(22) =230779071a(23) =632762424a(24) =1739387089

External references