Bit Rotation 2

Let n = 2^s, where $s$ is a non-negative integer. For each integer $i$ from $0$ to n-1, define the value a_i as follows. Let b_{s-1}\ldots b_1b_0 be the binary representation of $i$, padded on the left with zeros to have exactly $s$ bits if necessary. Reverse these bits to obtain b_0b_1\ldots b_{s-1}. Then a_i is the integer whose binary representation is b_0b_1\ldots b_{s-1}.

For example, if s = 3 and i = 3, the binary representation is 011_2, its reverse is 110_2, and thus if s = 3, a_3 = 6.

You are required, for a given $s$, to efficiently answer queries about the sum a_l + a_{l+1} + \ldots + a_r modulo $1000000007$.