18693

Appears in sequences

• Numbers n such that 5*10^n + 8*R_n - 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.at n=11A103022
• Odd numbers m for which A379113(m^2) > 1, i.e., k = m^2 has a proper unitary divisor d > 1 such that A048720(A065621(sigma(d)),sigma(k/d)) is equal to sigma(k).at n=37A379122
• Numbers k such that k - A067666(k) is a square.at n=37A386304