Expansion of tanh(tan(tan(x))).A009808Expansion of tanh(tan(tan(x))).Terms a(0) =1a(1) =2a(2) =8a(3) =-400a(4) =-54016a(5) =-6545408a(6) =-886739968a(7) =-130488590336External referencesoeis: A009808