a(n) = Euler(2*n)*binomial(4*n,2*n).A214445a(n) = Euler(2*n)*binomial(4*n,2*n).Terms a(0) =1a(1) =-6a(2) =350a(3) =-56364a(4) =17824950a(5) =-9334057876External referencesoeis: A214445