sech(sec(x)-sech(x))=1-12/4!*x^4+1568/8!*x^8+6840768/12!*x^12...

A013515

sech(sec(x)-sech(x))=1-12/4!*x^4+1568/8!*x^8+6840768/12!*x^12...

Terms

    a(0) =1a(1) =-12a(2) =1568a(3) =6840768a(4) =-41485549312

External references