20118

Appears in sequences

• Number of unrooted triangulations of the disk with n interior nodes and 3 nodes on the boundary.at n=8A002713
• Numbers k such that sigma(k+1) divides sigma(k), where sigma(k) is the sum of positive divisors of k.at n=28A058073
• Non-palindromic number and its reversal are both multiples of 14.at n=37A062913
• Numbers k such that gcd(sigma(k), sigma(k+1)) > k.at n=39A066025
• Average of 4 primes where the integer Schwarzian derivative is zero.at n=20A094903
• Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0) and consisting of n steps taken from {(-1, -1), (-1, 1), (-1, 0), (1, 0)}.at n=11A151261
• Numbers k such that sigma(k) = 2*sigma(k+1).at n=14A163193
• Array T(n,k) read by antidiagonals: T(n,k) is the number of [n,k]-triangulations in the plane, n >= 0, k >= 0.at n=44A169808
• Numbers k such that the average of the divisors of k and k+1 is the same.at n=11A238380
• a(n) = (Sum_{k=1..n} prime(k))^3 - (Sum_{k=1..n} prime(k)^3).at n=4A263170
• Numbers n such that Bernoulli number B_{n} has denominator 1806.at n=27A272139
• Numbers m such that the delta(m) = abs(h(m+1) - h(m)) is smaller than delta(k) for all k < m, where h(m) is the harmonic mean of the divisors of m.at n=5A335291
• Array read by antidiagonals: T(n,k) is the number of unrooted 3-connected triangulations of a disk with n interior nodes and k nodes on the boundary, n >= 1, k >= 3.at n=35A342053
• Numbers k such that k and k+1 have the same average of unitary divisors.at n=22A349222
• Numbers m such that tau(m) = 2 * tau(m + 1) and simultaneously sigma(m) = 2 * sigma(m + 1), where tau(k) = A000005(k) and sigma(k) = A000203(k).at n=0A353034
• a(n) = Sum_{k=0..n} binomial(k+6,6) * binomial(k,n-k)^2.at n=6A377158
• Triangle read by rows: T(n,k) is the number of n-node connected unsensed planar maps with an external face and k triangular internal faces, n >= 3, 1 <= k <= 2*n - 5.at n=80A378103