21415

Appears in sequences

• Numbers n such that phi(reverse(n)) = sigma(n).at n=10A070835
• Number of partitions of n into numbers having in binary representation at most trailing zeros.at n=46A087750
• a(1) = 1; thereafter a(n) is always the smallest integer > a(n-1) not leading to a contradiction, such that any five consecutive digits in the sequence sum up to a prime.at n=41A152605
• Number of pairwise coprime compositions of n, where a singleton is not considered coprime unless it is (1).at n=22A337462
• Number of subsets of {1..n} such that it is possible to choose a different binary index of each element.at n=21A370636