210208

Appears in sequences

• arcsinh(arctan(x)*tan(x))=2/2!*x^2+40/6!*x^6-2688/8!*x^8+210208/10!*x^10...at n=4A012450
• G.f.: Product_{n>=1} ((1-x^n)/(1+x^n))^(2*n).at n=30A216406