68689595569domain: NAppears in sequencesNumbers k such that k and floor[k/3] are both squares; i.e., squares which remain squares when written in base 3 and last digit is removed.at n=11A055793G.f.: -(1-3*x^2-x^3)/(1+4*x-4*x^3-x^4).at n=19A097948Sin(arcsin(n) - 4 arccos(n))^2.at n=7A239610