/usr/include/seqan/sequence/ is in libseqan2-dev 2.3.2+dfsg2-4ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/seqan/sequence/adapt_array_pointer.h
/usr/include/seqan/sequence/adapt_stl_container.h
/usr/include/seqan/sequence/container_view.h
/usr/include/seqan/sequence/container_view_zip.h
/usr/include/seqan/sequence/iter_concat_virtual.h
/usr/include/seqan/sequence/segment_base.h
/usr/include/seqan/sequence/segment_infix.h
/usr/include/seqan/sequence/segment_prefix.h
/usr/include/seqan/sequence/segment_suffix.h
/usr/include/seqan/sequence/segment_utils.h
/usr/include/seqan/sequence/sequence_concatenator.h
/usr/include/seqan/sequence/sequence_forwards.h
/usr/include/seqan/sequence/sequence_interface.h
/usr/include/seqan/sequence/sequence_lexical.h
/usr/include/seqan/sequence/sequence_shortcuts.h
/usr/include/seqan/sequence/string_alloc.h
/usr/include/seqan/sequence/string_array.h
/usr/include/seqan/sequence/string_base.h
/usr/include/seqan/sequence/string_block.h
/usr/include/seqan/sequence/string_cstyle.h
/usr/include/seqan/sequence/string_packed.h
/usr/include/seqan/sequence/string_packed_old.h
/usr/include/seqan/sequence/string_set_base.h
/usr/include/seqan/sequence/string_set_concat_direct.h
/usr/include/seqan/sequence/string_set_dependent_generous.h
/usr/include/seqan/sequence/string_set_dependent_tight.h
/usr/include/seqan/sequence/string_set_owner.h
/usr/include/seqan/sequence/string_set_segment.h
/usr/include/seqan/sequence/string_set_view.h
/usr/include/seqan/sequence_journaled/journal_entries_sorted_array.h
/usr/include/seqan/sequence_journaled/journal_entry.h
/usr/include/seqan/sequence_journaled/sequence_journaled.h
/usr/include/seqan/sequence_journaled/sequence_journaled_iterator.h
/usr/include/seqan/sequence_journaled/sequence_journaled_iterator_fast.h