628292059136domain: NAppears in sequencesDenominator of ez(n-1)*n!/(4^n-2^n) where ez(n) is the n-th coefficient of sec(t)+tan(t) for n>0, a(0) = 1.at n=21A193473The denominators of the Bernoulli secant numbers at odd indices.at n=10A193476a(n) = denominator(n / (4^n - 2^n)) for n > 0 and a(0) = 1.at n=21A336899