23519

Appears in sequences

• "BGK" (reversible, element, unlabeled) transform of 2,1,1,1,...at n=25A032062
• The sum of the non-divisors of n (less than n) is a multiple of the sum of the divisors of n.at n=20A066860
• Numbers k such that sum of the divisors d of k divides 1 + 2 + ... + k = k(k+1)/2.at n=22A076617
• a(n) = n^3 - n^2 - n.at n=29A152015
• a(n) = 784*n - 1.at n=29A158399
• a(n) = 30*n^2 - 1.at n=27A158560
• Numbers n such that n' = p^2-1, with n = semiprime = p*q, n' is the arithmetic derivative of n. Also: semiprimes of the form p*(p^2-p-1).at n=5A190274
• T(n,k)=Majority value maps: number of nXk binary arrays indicating the locations of corresponding elements equal to at least half of their horizontal, diagonal and antidiagonal neighbors in a random 0..2 nXk array.at n=23A220922
• Majority value maps: number of 3 X n binary arrays indicating the locations of corresponding elements equal to at least half of their horizontal, diagonal and antidiagonal neighbors in a random 0..2 3 X n array.at n=4A220924
• Least solution x to the equation x' = (x+1)/n, where x' is the arithmetic derivative of x; -1 if no solution exists.at n=27A263927
• a(n) is the smallest k such that (n+1)*phi(k) = (n-1)*psi(k).at n=26A291932
• MM-numbers of crossing set partitions.at n=27A324324