/usr/share/doc/ruby-gsl/examples/sf/zetam1.rb is in ruby-gsl 2.1.0.3+dfsg1-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 | #!/usr/bin/env ruby
require("gsl")
s = GSL::Vector.linspace(1.05, 13, 100)
y = GSL::Sf::zetam1(s)
y.graph(s, "-C -l y -L 'Zeta function z(s)-1' -X s -Y 'z(s)-1' --toggle-rotate-y-label")
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