63116domain: NAppears in sequencesNumbers k such that 20*R_k + 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=21A056656Structured hexagonal anti-prism numbers.at n=30A100183Number of recursively bi-anti-transitive ordered rooted trees with n nodes.at n=13A358456