3187591domain: NAppears in sequencesa(n) = (42^n - 1)/41.at n=5A218745a(n) = 1 + sigma(n) + sigma(n)^2 + sigma(n)^3 + sigma(n)^4.at n=19A258978a(n) = 1 + sigma(n) + sigma(n)^2 + sigma(n)^3 + sigma(n)^4.at n=25A258978