53859domain: NAppears in sequencesNumber of nonempty subsets of {1,2,...,n} in which exactly 1/5 of the elements are <= (n-4)/2.at n=21A048065Row sums of triangle A178239.at n=39A178240Numbers k such that 3*R_k + 50 is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=19A256800