155041domain: NAppears in sequencesa(n) = Sum_{k=0..n} (k+1) * A026780(n, n-k).at n=12A027252Numbers n such that A229964(n) = 3.at n=41A229966a(n) = Sum_{k=0..n} binomial(k, 7*(n-k)).at n=22A306721a(n) = Sum_{k=0..floor(4*n/7)} binomial(k+2,4*n-7*k).at n=35A390219