115962domain: NAppears in sequencesNumber of ways to place 2 nonattacking wazirs on an n X n board.at n=21A172225G.f.: 1/(1 - x/(1 - x^2/(1 - x^5/(1 - x^12/(1 - x^29/(1 - x^70/(1 -...- x^Pell(n)/(1 -...)))))))), a continued fraction.at n=25A206743