example bar numbers are printed at all possible places:
@lilypond[verbatim,quote,relative=1]
-\override Score.BarNumber.break-visibility = #'#(#t #t #t)
+\override Score.BarNumber.break-visibility = ##(#t #t #t)
\set Score.currentBarNumber = #11
% Permit first bar number to be printed
\bar ""