A013339 sech(exp(x)-sec(x))=1-1/2!*x^2+1/4!*x^4+20/5!*x^5+23/6!*x^6...

1, 0, -1, 0, 1, 20, 23, -140, -975, -1656, 74751, 365640, 1284369, -26269412, -120532297, 1518753340, 37230940193, 312855107472, -1646816770497, -37424409392880, -167334452580383, 9798194248744356