a(n) = A086582(2^n-1) for n>=0.A086584a(n) = A086582(2^n-1) for n>=0.Terms a(0) =1a(1) =1a(2) =2a(3) =6a(4) =26a(5) =180a(6) =2512a(7) =95100a(8) =14252768a(9) =14386501644External referencesoeis: A086584