/usr/share/doc/libfann-doc/html/index/ is in libfann-doc 2.2.0+ds-3.
This file is owned by root:root, with mode 0o755.
..
/usr/share/doc/libfann-doc/html/index/Classes.html
/usr/share/doc/libfann-doc/html/index/Constants.html
/usr/share/doc/libfann-doc/html/index/Functions.html
/usr/share/doc/libfann-doc/html/index/Functions2.html
/usr/share/doc/libfann-doc/html/index/Functions3.html
/usr/share/doc/libfann-doc/html/index/Functions4.html
/usr/share/doc/libfann-doc/html/index/General.html
/usr/share/doc/libfann-doc/html/index/General2.html
/usr/share/doc/libfann-doc/html/index/General3.html
/usr/share/doc/libfann-doc/html/index/General4.html
/usr/share/doc/libfann-doc/html/index/General5.html
/usr/share/doc/libfann-doc/html/index/Types.html