218205281domain: NAppears in sequencesa(n) = 7*a(n-1) - 14*a(n-2) + 7*a(n-3), a(0)=0, a(1)=1, a(2)=5.at n=15A215008a(n) = Sum_{k=0..floor(n/7)} (-1)^k*binomial(n,7*k).at n=31A307041First term of n-th difference sequence of round((k*Pi)), k >= 0.at n=31A325846