Expansion of tanh(tan(x)^2)/2.A024280Expansion of tanh(tan(x)^2)/2.Terms a(0) =0a(1) =1a(2) =8a(3) =16a(4) =-9472a(5) =-1073024a(6) =-73802752a(7) =6179501056External referencesoeis: A024280