/usr/include/regina-normal/maths/ is in regina-normal-dev 5.1-2build1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/regina-normal/maths/approx.h
/usr/include/regina-normal/maths/cyclotomic.h
/usr/include/regina-normal/maths/integer.h
/usr/include/regina-normal/maths/matrix.h
/usr/include/regina-normal/maths/matrix2.h
/usr/include/regina-normal/maths/matrixops.h
/usr/include/regina-normal/maths/ncyclotomic.h
/usr/include/regina-normal/maths/ninteger.h
/usr/include/regina-normal/maths/nmatrix.h
/usr/include/regina-normal/maths/nmatrix2.h
/usr/include/regina-normal/maths/nmatrixint.h
/usr/include/regina-normal/maths/nperm-impl.h
/usr/include/regina-normal/maths/nperm.h
/usr/include/regina-normal/maths/nperm2.h
/usr/include/regina-normal/maths/nperm3.h
/usr/include/regina-normal/maths/nperm4.h
/usr/include/regina-normal/maths/nperm5.h
/usr/include/regina-normal/maths/npolynomial.h
/usr/include/regina-normal/maths/nprimes.h
/usr/include/regina-normal/maths/nrational.h
/usr/include/regina-normal/maths/nray.h
/usr/include/regina-normal/maths/numbertheory.h
/usr/include/regina-normal/maths/nvector.h
/usr/include/regina-normal/maths/perm-impl.h
/usr/include/regina-normal/maths/perm.h
/usr/include/regina-normal/maths/polynomial.h
/usr/include/regina-normal/maths/primes.h
/usr/include/regina-normal/maths/rational.h
/usr/include/regina-normal/maths/ray.h
/usr/include/regina-normal/maths/spec/
/usr/include/regina-normal/maths/spec/perm2.h
/usr/include/regina-normal/maths/spec/perm3.h
/usr/include/regina-normal/maths/spec/perm4.h
/usr/include/regina-normal/maths/spec/perm5.h
/usr/include/regina-normal/maths/vector.h