How hard is to compute $\Delta_{|V|}$? Let $G=(V,E)$ be a graph. Let $\Delta_k$ be the quantity defined in this question. Let $\mathcal{C}$ be the set of vertex covers of $G$. The following holds:

$$
|\mathcal{C}| = 2^{|V|} - \sum_{k = 2}^{|V|} \Delta_k \cdot 2^{|V|-k}
$$

Let us focus on $\Delta_{|V|}$.



Question

How hard is to compute $\Delta_{|V|}$?



Motivation

The quantity
$$\Delta_{|V|}\ \ mod\ \ 2$$
is the parity of the number of vertex covers of $G$. If such quantity is $0$ then $|\mathcal{C}|$ is even, otherwise $|\mathcal{C}|$ is odd.

Therefore (forgive me if I'm wrong):


Being able to compute $\Delta_{|V|}$ in polynomial time implies $\mathbin{\oplus}$P = P.
$\Delta_{|V|}$ being $\#$P-hard to compute implies $\mathbin{\oplus}$P = PP. 


It seems that in both cases we would get an important result. Clearly there is a third option: computing $\Delta_{|V|}$ may be of intermediate counting complexity, strictly harder than FP but strictly easier than $\#$P-hard.

Update 08/01/2013 21:50

After reading again and more carefully T. Williams' answer to this question, my understanding is that such answer precisely proves that computing $\Delta_{|V|}$ is $\#$P-hard (because the constraint $[0,1,1,1]$ forces every node of $G$ to be present).

However, my second conclusion above does not hold: to conclude $\mathbin{\oplus}$P = PP, computing $\Delta_{|V|}\ \ mod\ \ 2$ should be $\#$P-hard. But the $\#$P-hardness of computing $\Delta_{|V|}$ is not known to imply that computing $\Delta_{|V|}\ \ mod\ \ 2$ is $\#$P-hard as well.

Only a more vague and harmless conclusion can be drawn, more or less along these lines: something which appear to be false from a practical point of view (i.e. Graph Isomorphism $\not\in$ P) would imply something already formally known to be true (i.e. computing $\Delta_{|V|}$ is $\#$P-hard).
As the OP pointed out in an update above, the second question about computing $\Delta_{|V|}$ is answered in this question.

The first question is about computing the parity of the number of vertex covers. This problem is $\bigoplus$P-hard even for planar 3-regular graphs.  See Section 4.1 of this paper (particularly Corollary 4.2).

First, the notation for the corresponding Holant problem is Pl-$\bigoplus$Holant$([0,1,1]|[1,0,0,1])$.  Since there is a 1-to-1 correspondence between vertex covers and independent sets, sometimes people also refer to the Holant expression for independent set (in this case, $\bigoplus$Holant$([1,1,0]|[1,0,0,1])$) as though it were the vertex cover problem.

Second, I don't know why they called this problem $\bigoplus$3/2-Bip-VC (that is, why "3/2-Bip").  As I said above, this Holant expression is for the counting of vertex covers (equivalently, independent sets) in 3-regular graphs.