223948800domain: NAppears in sequencesa(n) = 10(n+1)^3*(2n+1)(7n+5)^2.at n=7A109121a(n) = phi(n!!) where phi is the Euler totient function. In other words, a(n) = A000010(A006882(n)).at n=18A129335Number of 0..n arrays of length 7 with each element unequal to at least one neighbor, starting with 0.at n=23A221466