19192151164domain: NAppears in sequencesRelated to Euler numbers, expansion of e.g.f. sec(x)*tan^2(x).at n=12A002735Number of down-up permutations of n+3 starting with n+1.at n=14A006212a(n) = n! * [x^n] 2*(tan(x))^2*(sec(x) + tan(x)).at n=14A164575