571781

Appears in sequences

• a(n) = 7*a(n-1) - 14*a(n-2) + 7*a(n-3) with a(0)=0, a(1)=1, a(2)=7.at n=10A217274
• a(n) = Sum_{k=0..floor(n/7)} (-1)^k*binomial(n,7*k).at n=23A307041