A012997 exp(arctan(x)+tan(x))=1+2*x+4/2!*x^2+8/3!*x^3+16/4!*x^4+72/5!*x^5...

1, 2, 4, 8, 16, 72, 544, 3040, 11008, 64896, 1060224, 10595840, 38065152, 87854080, 9708670976, 170663275520, 276991311872, -13108265091072, 283899182678016, 9548887177330688, -9456062364418048