12111126301domain: NAppears in sequencesa(n) = (1 - (-7)^n)/8.at n=12A014989Gaussian binomial coefficient [ n,12 ] for q=-7.at n=1A015430a(n) = 6*a(n-1) + 7*a(n-2), a(0) = 0, a(1) = 1.at n=13A015552Cyclotomic polynomials at x=7.at n=26A019325Cyclotomic polynomials at x = -7.at n=13A020506a(n) = Sum_{j=0..12} (-n)^j.at n=7A266229