Expansion of tan(tanh(x)*cos(x)).A009720Expansion of tan(tanh(x)*cos(x)).Terms a(0) =1a(1) =-3a(2) =-43a(3) =2009a(4) =6313a(5) =-9872907a(6) =760322045a(7) =105243758801External referencesoeis: A009720