A012833 sech(sec(x)*arcsinh(x))=1-1/2!*x^2-3/4!*x^4-45/6!*x^6+2457/8!*x^8...
1, -1, -3, -45, 2457, -36825, 12566037, -1732392389, 313988548273, -92368244011185, 30231378922437805, -12317648529216417629, 6168347852710380187977, -3616136826996686827399305
Offset: 0