21975

Appears in sequences

• Floor[ concatenation of n+4, n+3, n+2, n+1 and n divided by 5].at n=6A075006
• Table with g.f. [1-x*n-sqrt(x^2*n^2-2*n*x+1+4*x^2-4*x)]/(2*x).at n=51A128888
• Number of composites removed in each step of the Sieve of Eratosthenes for 10^7.at n=17A227155
• Number of different positions in which a square with side length k, 1 <= k <= n - floor(n/3), can be placed within a bi-symmetric triangle of 1 X 1 squares of height n.at n=44A241526
• a(n) = number of triangles with integer sides i <= j <= k with radius of circumcircle <= n.at n=33A331229
• Numbers k such that k divides the sum of digits in factorial base of all numbers from 1 to k.at n=24A333702
• Number of geodetic graphs with n unlabeled vertices.at n=11A337179