Can't import PostgreSQL10 dump into 9.6 database

Judging from the error messages you show, you'll have to edit the SQL dump and remove all occurrences of AS integer from all CREATE SEQUENCE statements.

The AS data_type clause of CREATE SEQUENCE is new in PostgreSQL v10, and older server versions will not understand it.

Following @"Laurenz Albe" suggestion, here's a python3 snippet can be used to downgrade a 10.x pg_dump script for 9.x:

#!/usr/bin/env python3
import sys

#
#  Downgrades pg_dump 10 script to 9.x
#  removing 'AS integer' from 'CREATE SEQUENCE' statement
#
#  Usage:
#       $ python3 pgdump_10_to_9.py < test10.sql > test9.sql
#  or:
#       $ cat test10.sql | ./pgdump_10_to_9.py > test9.sql
#
#  To obtain a compressed 9.x sql script from a compressed 10 sql script:
#
#       $ gunzip -c test10.sql.gz | ./pgdump_10_to_9.py | gzip > test9.sql.gz
#

inside_create_sequence = False
for row in sys.stdin.readlines():

    if inside_create_sequence and row.strip().lower() == 'as integer':
        pass
    else:
        print(row, end='', flush=True)

    inside_create_sequence = row.strip().startswith('CREATE SEQUENCE ')