How to build a btree index with integer values on jsonb data?

How can I transform the following definition to index pubyear as
integer and not text?

CREATE INDEX pubyear_idx
ON some_table_where_data_field_is_of_type_jsonb USING btree
((((((data -> 'REC'::text) -> 'static_data'::text) ->
'summary'::text) -> 'pub_info'::text) ->> '@pubyear'::text) COLLATE
pg_catalog."default");

While I can cast the value in a SELECT statement to integer I have
been able to do the same while creating the index.

Why btree index? I want to do queries like

select stuff from sometable where pubyear between 2015 and 2018;

Regards
Johann
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