2175865domain: NAppears in sequencesExpansion of (1+x+x^2)/((1-x^2)*(1-2*x-x^2)); a Pellian-related sequence.at n=16A114697Indices of triangular numbers (A000217) that are also decagonal (A001107).at n=9A133218Numbers k such that 2 * A000217(k) + 1 is triangular.at n=17A216134Sequences A006452 and A216134 interlaced.at n=35A216162