533203385domain: NAppears in sequencesa(0) = 1; for n > 0, a(n) = (-1)^(n+1)*B(2n)*Product_{prime p<=2n+1} p where B(2n) denotes the (2n)-th Bernoulli number.at n=9A123536a(n) = B(n,1)*(n+1)# where B(n,x) are the Bernoulli polynomials and n# are the primorial numbers A034386.at n=18A292899