280063domain: NAppears in sequencesa(n) = 6^n + 2^n - 1.at n=7A155589Numbers that can be written in exactly three different ways as s_1^x_1 + ... + s_t^x_t, with 1 < s_1 < ... < s_t and {s_1,..., s_t} = {x_1,..., x_t} for some t > 0.at n=31A386967