a(n) = Sum_{d|n} -(-1)^d * 2^(n^2/d) * d.A262826a(n) = Sum_{d|n} -(-1)^d * 2^(n^2/d) * d.Terms a(0) =2a(1) =8a(2) =536a(3) =64960a(4) =33554592a(5) =68718964352External referencesoeis: A262826