123018750

Appears in sequences

• Numbers n that form a Pythagorean quadruple with n', n'' and sqrt(n^2 + n'^2 + n''^2), where n' and n'' are the first and the second arithmetic derivative of n.at n=18A230543
• Numbers which have identical primes in n and d(n) but are not refactorable.at n=25A235525