119930domain: NAppears in sequencesa(n) = 3*a(n-1) + 24*a(n-2) + a(n-3), with a(0)=0, a(1)=2, and a(2)=7.at n=7A217069Numbers k such that 9*R_k + 7*10^k - 2 is prime, where R_k = 11...11 is the repunit (A002275) of length k.at n=12A259134Expansion of Product_{1 <= i < j} 1/(1 - x^(i*j)).at n=49A321285