336585600domain: NAppears in sequencesa(n) = (n+1)*binomial(n+1,8).at n=24A027768If X_1,...,X_n is a partition of a 2n-set X into 2-blocks then a(n) is equal to the number of 7-subsets of X containing none of X_i, (i=1,...n).at n=24A130813