Oracle 11g Release 2

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WITH yourTable AS (
    SELECT 72 AS PC_ID, 'bob' AS USER_NAME, timestamp '2020-08-10 09:00:00' AS LOGIN_TIME FROM dual UNION ALL
    SELECT 72, 'bob',  timestamp '2020-08-10 13:30:00' FROM dual UNION ALL
    SELECT 72, 'bob',  timestamp '2020-08-11 09:00:00' FROM dual UNION ALL
    SELECT 72, 'jane', timestamp '2020-08-12 08:00:00' FROM dual UNION ALL
    SELECT 72, 'jane', timestamp '2020-08-13 09:00:00' FROM dual UNION ALL
    SELECT 72, 'jane', timestamp '2020-08-13 14:30:00' FROM dual UNION ALL
    SELECT 72, 'bob',  timestamp '2020-08-14 08:00:00' FROM dual UNION ALL
    SELECT 72, 'bob',  timestamp '2020-08-15 08:00:00' FROM dual UNION ALL
    SELECT 72, 'bob',  timestamp '2020-08-16 08:00:00' FROM dual UNION ALL
    SELECT 72, 'bob',  timestamp '2020-08-17 08:00:00' FROM dual
),
cte AS (
    SELECT t.*, ROW_NUMBER() OVER (PARTITION BY PC_ID ORDER BY LOGIN_TIME) rn1,
                ROW_NUMBER() OVER (PARTITION BY PC_ID, USER_NAME ORDER BY LOGIN_TIME) rn2
    FROM yourTable t
)

SELECT
    PC_ID,
    USER_NAME,
    MIN(LOGIN_TIME) AS FIRST_LOGIN,
    MAX(LOGIN_TIME) AS LAST_LOGIN
FROM cte
GROUP BY
    PC_ID,
    USER_NAME,
    (rn1 - rn2)
ORDER BY
    MIN(LOGIN_TIME);

PC_ID	USER_NAME	FIRST_LOGIN	LAST_LOGIN
72	bob	10-AUG-20 09.00.00.000000000 AM	11-AUG-20 09.00.00.000000000 AM
72	jane	12-AUG-20 08.00.00.000000000 AM	13-AUG-20 02.30.00.000000000 PM
72	bob	14-AUG-20 08.00.00.000000000 AM	17-AUG-20 08.00.00.000000000 AM