20. The page numbers range from 1 to 64. Pages on double sheets are arranged as follows:

$$
\begin{aligned}
& 1-\bar{h}-1,2,63,64 ; \\
& 2-\bar{и}-3,4,61,62 ;
\end{aligned}
$$

16th-31, 32, 33, 34. Since in the sequence the sums of numbers equidistant from the ends are the same, i.e., $1+64=2+63=\ldots=32+33$, the sums of the numbers indicating the page numbers of the double sheets are the same, namely $65+65=130$.
20. A magazine consists of 16 nested double sheets. On which double sheet will the sum of the numbers indicating the page numbers be the greatest?