123797

Appears in sequences

• Concatenation of n in base 2 up to base 10 and n in base 10 down to base 2 is prime, all numbers are interpreted as decimals.at n=18A054258
• Numbers k such that sigma(k+1) = 2*sigma(k).at n=25A067081
• a(n) is the smallest integer m such that A039995(m)=n.at n=30A094535