generate_series not working in single user mode
The INSERT ... VALUES (...), (...), ... ; syntax can accept multiple rows but you can't put a table generating function inside a row.

You need to use the INSERT .. SELECT .. FROM .. ; syntax and put the table generating function in the FROM clause:

insert into t1 (i, j) 
select g.i, g.i 
from generate_series(1, 200000) as g(i) ;