210020

Appears in sequences

• Numbers k such that the square of k contains sigma(k) as a substring, in base 10.at n=21A113654
• Numbers encoded in an alternate, sometimes more compact, binary system with a third, dual-purpose, prefix/delimiter symbol not always required.at n=30A140116
• Number of (n+1) X (n+1) 0..3 arrays with every 2 X 2 subblock having its diagonal sum differing from its antidiagonal sum by 4 (constant-stress 1 X 1 tilings).at n=12A235281
• Number of edges formed inside a square with edge length 1 by the straight line segments mutually connecting all vertices and points that divide the sides into segments with lengths equal to the Farey series of order n = A006842(n,k)/A006843(n,k), k = 1..A005728(n).at n=5A358888