Let 2007+4v=κ2, κ∈N. Then
κ2−4v=2007⇔κ2−22v=2007⇔(κ−2v)(κ+2v)=1⋅3⋅3⋅223.
Since κ−2v<κ+2v, last equality is equivalent to the systems
{κ−2v=1κ+2v=2007 or {κ−2v=3κ+2v=669 or {κ−2v=9κ+2v=223(Σ1) or (Σ2) or (Σ3)
Now we have
(Σ1)⇔{κ−2v=1κ+2v=2007⇔{2κ=20082⋅2v=2006⇒2v=1003, absurd..
(Σ2)⇔{κ−2v=3κ+2v=669⇔{2κ=6722⋅2v=666⇒2v=333, absurd.
(Σ3)⇔{κ−2v=9κ+2v=223⇔{2κ=2322⋅2v=214⇒2v=107, absurd.
Therefore, there are not natural numbers v such that 2007+4v is a perfect square.