70021domain: NAppears in sequencesComposite numbers k such that b^k == b (mod sigma(k)) for every integer b.at n=4A277286Reflection of the concatenation of the previous two terms minus the previous term.at n=5A345143E.g.f. satisfies A(x) = (exp(x) - 1) * exp(3 * A(x)).at n=5A357336