45812722347domain: NAppears in sequencesGaussian binomial coefficient [n, 2] for q = 2.at n=19A006095M(M-1)/6, where M is Mersenne prime A000668(n).at n=6A139226a(n) = 6*a(n-1) - 8*a(n-2) + 1 for n > 1; a(0) = 1, a(1) = 7.at n=17A171477