7091569

Appears in sequences

• Perfect squares which can be written neither as a^2+b^2, nor as a^2+2*b^2, nor as a^2+3*b^2, nor as a^2+7*b^2, with a > 0 and b > 0.at n=24A216408
• Numbers n such that sigma(n) and sigma(n^2) are primes.at n=6A232444
• Numbers n such that 2n-1 and sigma(n) are both primes.at n=25A249902
• Numbers n such that both sigma(n) and sigma(n) - 2 are primes.at n=14A274963