2039499domain: NAppears in sequencesE.g.f. S(x) satisfies: C(x)^2 + 2*S(x)^2 = 1 such that S'(x) = C(x)^2 - S(x)*C(x) and C'(x) = 2*S(x)^2 - 2*S(x)*C(x), where C(x) is described by A279841.at n=9A279842