bpo-36189: Fixing typo in tutorial introduction (GH-13090)

diff --git a/Doc/tutorial/introduction.rst b/Doc/tutorial/introduction.rst
index 3e0c995..a4dbd63 100644
--- a/Doc/tutorial/introduction.rst
+++ b/Doc/tutorial/introduction.rst
@@ -383,7 +383,7 @@
    >>> squares
    [1, 4, 9, 16, 25]
 
-Like strings (and all other built-in :term:`sequence` type), lists can be
+Like strings (and all other built-in :term:`sequence` types), lists can be
 indexed and sliced::
 
    >>> squares[0]  # indexing returns the item