E.g.f. sqrt(1+tan(2*x)).

Terms

a(0) =1a(1) =1a(2) =-1a(3) =11a(4) =-47a(5) =601a(6) =-5521a(7) =86771a(8) =-1296287a(9) =25482481a(10) =-527699041a(11) =12800059931a(12) =-335639304527