810600392196domain: NAppears in sequencesa(n) = 21*a(n-1) + a(n-2), starting with a(0) = 2 and a(1) = 21.at n=9A090310a(n) = n*(n^2 + 3)*(n^6 + 6*n^4 + 9*n^2 + 3).at n=21A261574