a(n) = f(f(n+1)) - f(f(n)), where f(m) = 2^m.A111403a(n) = f(f(n+1)) - f(f(n)), where f(m) = 2^m.Terms a(0) =2a(1) =12a(2) =240a(3) =65280a(4) =4294901760External referencesoeis: A111403