-4251528domain: ZAppears in sequencesExpansion of 1/(3*x^2 - 3*x + 1)^2.at n=21A115052Triangle read by rows: T(0,0) = 1; T(n,k) = 3 T(n-1,k) - 2 * T(n-3,k-1) for k = 0..floor(n/3); T(n,k)=0 for n or k < 0.at n=41A317502