6444873domain: NAppears in sequencesNumbers k such that t(k) = t(k+1) where t(k) = tau(k) + sigma(k) = A007503(k) is the number of subgroups of the dihedral group of order 2k.at n=29A322256Numbers k such that k and k+1 have the same number and sum of divisors but a different number of distinct prime factors.at n=4A350800