2069613

Appears in sequences

• a(n) = Sum_{k=0..floor(n/2)} binomial(n-k, k-1) * 4^(k-1).at n=17A099580
• Odd integers k such that sigma(k)^2 is divisible by k.at n=8A263983
• Integers x such that sigma(x)^2 - 3*x^2 is a square.at n=27A385810