Expansion of sin(tanh(sin(x))).A009520Expansion of sin(tanh(sin(x))).Terms a(0) =1a(1) =-4a(2) =68a(3) =-2528a(4) =160400a(5) =-15384128a(6) =2066458176a(7) =-369136141824External referencesoeis: A009520