21029
domain: N
Appears in sequences
- Numbers k such that k! - (k-1)! - 1 is prime.at n=26A049433
- Beach-Williams Pell numbers of type k^2 + 4.at n=4A212083
- Number of solutions to n = Sum_{i=1..pi(n-1)} c(i)*p(i) with c(i) in {-1,0,1}, p(n) = n-th prime and pi = A000720.at n=45A215222
- Numbers n where tau(n) and n-tau(n) are perfect squares, with tau(n) the number of divisors of n (A000005).at n=37A245197
- Number of positive solutions to x^2+y^2+z^2 <= n^2.at n=35A253663
- Number of aperiodic necklaces (Lyndon words) with k<=5 black beads and n-k white beads.at n=41A277629
- Markoff spectrum N^(5)(Lambda).at n=26A293173
- Numbers that are palindromic in base 2 and base 16.at n=38A340559
- Semiprimes of the form k^2 + 4.at n=31A360741