with t1(nn, name, number) as (
    values
    (1, 'a', 1),
    (2, 'a', 2),
    (3, 'a', 3),
    (4, 'a', 2),
    (5, 'a', 3),
    (6, 'b', 1),
    (7, 'b', 3),
    (8, 'b', 2),
    (9, 'b', 3),
    (10, 'b', 1)
)
select t1_prev, t1, t1_next from t1
    join t1 as t1_prev on t1.name = t1_prev.name and t1_prev.number + 1 = t1.number and t1_prev.nn < t1.nn
    join t1 as t1_next on t1.name = t1_next.name and t1.number + 1 = t1_next.number and t1.nn < t1_next.nn
;

 t1_prev |   t1    | t1_next 
---------+---------+---------
 (1,a,1) | (2,a,2) | (3,a,3)
 (1,a,1) | (4,a,2) | (5,a,3)
 (1,a,1) | (2,a,2) | (5,a,3)
 (6,b,1) | (8,b,2) | (9,b,3)
(4 строки)