man: use unicode superscripts to indicate the exponent

man/sd_journal_next.xml

@@ -80,7 +80,7 @@
     <para><function>sd_journal_next_skip()</function> and
     <function>sd_journal_previous_skip()</function> advance/set back the read pointer by multiple
     entries at once, as specified in the <varname>skip</varname> parameter. The <varname>skip</varname>
-    parameter must be less than or equal to 2147483647 (2^31-1).</para>
+    parameter must be less than or equal to 2147483647 (2³¹-1).</para>
 
     <para>The journal is strictly ordered by reception time, and hence
     advancing to the next entry guarantees that the entry then

man/systemd-journald.service.xml

@@ -71,7 +71,7 @@
     </para>
 
     <para>Log data collected by the journal is primarily text-based but can also include binary data where
-    necessary. Individual fields making up a log record stored in the journal may be up to 2^64-1 bytes in size.</para>
+    necessary. Individual fields making up a log record stored in the journal may be up to 2⁶⁴-1 bytes in size.</para>
 
     <para>The journal service stores log data either persistently below <filename>/var/log/journal</filename> or in a
     volatile way below <filename>/run/log/journal/</filename> (in the latter case it is lost at reboot). By default, log

man/systemd.net-naming-scheme.xml

@@ -386,7 +386,7 @@
 
           <para>Some firmware and hypervisor implementations report unreasonably high numbers for the onboard
           index. To prevent the generation of bogus onbard interface names, index numbers greater than 16381
-          (2^14-1) were ignored. For s390 PCI devices index values up to 65535 (2^16-1) are valid. To account
+          (2¹⁴-1) were ignored. For s390 PCI devices index values up to 65535 (2¹⁶-1) are valid. To account
           for that, the limit was increased to 65535.</para>
 
           <para>The udev rule <varname>NAME=</varname> replaces <literal>:</literal>,