26803domain: NAppears in sequencesNumber of tilings of a 21 X n rectangle using 3n heptominoes of shape I.at n=15A251076Expansion of 1/(1 - x - x^3/(1 - x^5 - x^7/(1 - x^9 - x^11/(1 - x^13 - x^15/(1 - ...))))), a continued fraction.at n=26A292800