70190

Appears in sequences

• Numbers k such that phi(k) = sigma(k+1) - sigma(k-1).at n=20A066155
• a(n) = gpf(a(n-3))*gpf(a(n-2)) + gpf(a(n-1)), with a(1)=a(2)=1 and a(3)=2 and where gpf(n) is the greatest prime dividing n, A006530(n).at n=22A258804