DECLARE @N INT = 1001;
WITH Numbers AS (
    SELECT 2 AS num
    UNION ALL
    SELECT num + 1
    FROM Numbers
    WHERE num + 1 <= @N
),
Primes AS (
    SELECT num
    FROM Numbers n
    WHERE NOT EXISTS (
        SELECT 1
        FROM Numbers d
        WHERE d.num < n.num
          AND d.num > 1
          AND n.num % d.num = 0
    )
)
SELECT STRING_AGG(CAST(num AS VARCHAR), '&') AS primes
FROM Primes
OPTION (MAXRECURSION 0);