61230

Appears in sequences

• Numbers n such that the denominator of the 2n-th Bernoulli number is divisible by n but sum_{d|n} sigma(d)/phi(d) is not an integer.at n=23A099008
• Numbers k such that (8*10^k + 67)/3 is prime.at n=24A281732
• Numbers k such that sigma_2(k^2 + 1) == 0 (mod k).at n=41A360105