21690

Appears in sequences

• Number of rooted toroidal maps with 2 faces and n vertices and without separating cycles or isthmuses.at n=7A006422
• Numerators of continued fraction convergents to sqrt(905).at n=2A042748
• Total number of parts in all partitions of n plus the sum of largest parts in all partitions of n plus the number of partitions of n plus n.at n=23A225610
• Triangle read by rows: T(n,k) is the number of rooted toroidal maps with n edges and k faces and without separating cycles or isthmuses, n >= 2, k = 1..n-1.at n=37A343090
• Triangle read by rows: T(n,k) is the number of rooted toroidal maps with n edges and k faces and without separating cycles or isthmuses, n >= 2, k = 1..n-1.at n=43A343090
• Numbers k for which phi(k) = phi(k''), where phi is the Euler totient function (A000010) and k'' the second arithmetic derivative of k (A068346).at n=37A352331