6444032domain: NAppears in sequencesa(n) = (n+1)*binomial(n+1,5).at n=27A027765If X_1,...,X_n is a partition of a 2n-set X into 2-blocks then a(n) is equal to the number of 5-subsets of X containing none of X_i, (i=1,...n).at n=27A130811