2116116

Appears in sequences

• Numbers k such that (k, phi(k), sigma(k)) lies on a sphere with integral radius centered at the origin, i.e., k^2 + phi(k)^2 + sigma(k)^2 is a square.at n=28A066785
• Expansion of Product_{k>=1} (1 + x^k)/(1 - 2*x^k).at n=18A264685