\text{Let} ~ W_p ~ \text{be a Wagstaff number of the form :} W_p = \frac{2^p+1}{3}~, \text{where}~p>3
\text {Let's define }~S_0~ \text{as :}
S_0 =
\begin{cases}
3/2, & \text{if } p \equiv 1 \pmod 4 \\
11/2, & \text{if } p \equiv 1 \pmod 6 \\
27/2, & \text{if} ~p \equiv 11 \pmod {12}...