3341637

Appears in sequences

• Numbers of the form (9^i)*(13^j), with i, j >= 0.at n=26A108748
• Numbers k such that sigma(tau(k)) = rad(k).at n=22A173582
• Expansion of g.f. (1-4*x)/(1-13*x).at n=6A196663
• Odd numbers k such that A173557(k) divides nonzero A051709(k).at n=23A345054
• Odd numbers of the form p^(1+4k) * r^2, where p is prime of the form 1+4m, k > 0, r > 1, and gcd(p,r) = 1.at n=12A386428
• a(n) is the least k that is a multiple of d=A240991(n), with abundancy ratio sigma(k)/k equal to (sigma(d)+1)/d, or -1 if no such k exists.at n=17A387405
• Numbers k such that sigma(A253560(k)) / A253560(k) is equal to (sigma(k)+1) / k, where A253560(k) = k multiplied by its largest prime factor.at n=35A387406