-2170560domain: ZAppears in sequencesExpansion of e.g.f. C(x,k) satisfying C(x,k) = cos( x*cos(k*x*C(x,k)) ), as a triangle read by rows.at n=18A370330Expansion of e.g.f. D(x,k) satisfying D(x,k) = cos( k*x*cos(x*D(x,k)) ), as a triangle read by rows.at n=17A370332