/usr/share/doc/libmath++-doc/html/ftv2lastnode.png is in libmath++-doc 0.0.4-5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libmath++-doc/html/ftv2blank.png
/usr/share/doc/libmath++-doc/html/ftv2blank.png