# Warning: the following program has been naively adapted from the PostgresQL but
# should be further modified to ensure correctness, e.g. by adding a counter
CREATE or replace FUNCTION fib(n) AS (
    WITH RECURSIVE fibonacci(current, previous) AS (

    SELECT 0::UHUGEINT, 1::UHUGEINT
    -- another possibility: SELECT 0::FLOAT, 1::FLOAT
    UNION ALL
        SELECT previous + current, current FROM fibonacci
    )
    SELECT current FROM fibonacci
    LIMIT 1 OFFSET n
);

# Example
select fib(100);