a(n) = A000364(n) * (3^(2*n+1) + 1)/4.A002437a(n) = A000364(n) * (3^(2*n+1) + 1)/4.Terms a(0) =1a(1) =7a(2) =305a(3) =33367a(4) =6815585a(5) =2237423527External referencesoeis: A002437