a(n) = A255466(2^n-1).

Terms

a(0) =1a(1) =6a(2) =26a(3) =110a(4) =450a(5) =1822a(6) =7330a(7) =29406a(8) =117794a(9) =471518a(10) =1886754a(11) =7548382a(12) =30196258a(13) =120790494a(14) =483172898a(15) =1932713438a(16) =7730897442a(17) =30923677150a(18) =123694883362a(19) =494779882974