95613domain: NAppears in sequencesNumbers of the form m = p1 * p2 * p3 * p4 where for each d|m we have (d+m/d)/2 prime and p1 < p2 < p3 < p4 each prime.at n=15A128285Regular triangle where T(n,k) is the number of pairs of set partitions of {1,...,n} with join of length k.at n=23A318392