190399

Appears in sequences

• Numbers k such that sigma(phi(sigma(k))) = phi(k).at n=22A066465
• Numbers y such that 19*y^2 + 81 is a square.at n=11A167709
• Subsequence of A167709 whose indices are congruent to 1 mod 5, i.e., a(n) = A167709(5*n+1).at n=2A167822
• Expansion of (1 - 2*x - sqrt(1 - 8*x + 8*x^2))/(2*x*(1-x)).at n=8A174347