I am not qualified to answer on the OOM issue but why are you joining the same table (outputrequest) 4 times (using an identical join condition)?
This essentially does a cross join, if an input_sequence value has say, 1000 related rows in outputrequest, you will be getting 1000^4 rows in the result set.
The query itself runs fine in a reasonable time with enable_parallel_hash = 'off'. I see two problems - one is the wrong execution plan (right after running analyze), the second and the most important is the huge memory usage (far exceeding work_mem and shared buffers) leading to OOM.
