288086

Appears in sequences

• Numbers n such that phi(phi(n)) + sigma(sigma(n)) is an 8th power.at n=6A172465
• a(0)=0, a(1)=1, a(n) = min{5 a(k) + (5^(n-k)-1)/4, k=0..(n-1)} for n>=2.at n=30A259669