21640

Appears in sequences

• Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 73.at n=35A031571
• Number of upward triangles in a Star of David matchstick arrangement of size n.at n=16A045950
• First occurrence of n consecutive n's in the decimal expansion of sqrt(3).at n=4A224874
• Number of (n+1) X (6+1) 0..1 arrays with no 2 X 2 subblock having the sum of its diagonal elements greater than the maximum of its antidiagonal elements.at n=12A251126
• Numbers k such that Bernoulli number B_{k} has denominator 13530.at n=13A295587
• Number of compositions (ordered partitions) of n into octagonal numbers (A000567).at n=51A322800
• Number of integer compositions of n that are not the first sums of any finite nonnegative sequence.at n=15A391645