12222222221domain: NAppears in sequencesExpansion of g.f. x*(1+10*x)/((1-x)*(1-10*x^2)).at n=20A094623Expansion of g.f. x*(1+11*x+x^2)/((1-x)*(1+x)*(1-10*x^2)).at n=20A094624a(n) = n 2's sandwiched between two 1's.at n=9A132583