with field as
(
select 'a1' s_name from dual union all
select 'a2' s_name from dual union all
select 'a3' s_name from dual union all
select 'a4' s_name from dual union all
select 'a5' s_name from dual union all
select 'a6' s_name from dual union all
select 'a7' s_name from dual union all
select 'a8' s_name from dual union all

select 'b1' s_name from dual union all
select 'b2' s_name from dual union all
select 'b3' s_name from dual union all
select 'b4' s_name from dual union all
select 'b5' s_name from dual union all
select 'b6' s_name from dual union all
select 'b7' s_name from dual union all
select 'b8' s_name from dual union all

select 'c1' s_name from dual union all
select 'c2' s_name from dual union all
select 'c3' s_name from dual union all
select 'c4' s_name from dual union all
select 'c5' s_name from dual union all
select 'c6' s_name from dual union all
select 'c7' s_name from dual union all
select 'c8' s_name from dual union all

select 'd1' s_name from dual union all
select 'd2' s_name from dual union all
select 'd3' s_name from dual union all
select 'd4' s_name from dual union all
select 'd5' s_name from dual union all
select 'd6' s_name from dual union all
select 'd7' s_name from dual union all
select 'd8' s_name from dual union all

select 'e1' s_name from dual union all
select 'e2' s_name from dual union all
select 'e3' s_name from dual union all
select 'e4' s_name from dual union all
select 'e5' s_name from dual union all
select 'e6' s_name from dual union all
select 'e7' s_name from dual union all
select 'e8' s_name from dual union all

select 'f1' s_name from dual union all
select 'f2' s_name from dual union all
select 'f3' s_name from dual union all
select 'f4' s_name from dual union all
select 'f5' s_name from dual union all
select 'f6' s_name from dual union all
select 'f7' s_name from dual union all
select 'f8' s_name from dual union all

select 'g1' s_name from dual union all
select 'g2' s_name from dual union all
select 'g3' s_name from dual union all
select 'g4' s_name from dual union all
select 'g5' s_name from dual union all
select 'g6' s_name from dual union all
select 'g7' s_name from dual union all
select 'g8' s_name from dual union all

select 'h1' s_name from dual union all
select 'h2' s_name from dual union all
select 'h3' s_name from dual union all
select 'h4' s_name from dual union all
select 'h5' s_name from dual union all
select 'h6' s_name from dual union all
select 'h7' s_name from dual union all
select 'h8' s_name from dual
)
select /*+FIRST_ROWS */ steps from
(
select
t.*, level lvl, SYS_CONNECT_BY_PATH(s_name, '/') steps
from
(
select
row_number() over(order by s_name) id, f.s_name, row_number() over(order by s_name) parent_id
from
field f
) t
where
level <= 64
connect by NOCYCLE
(
(
(id = prior parent_id + 10 and mod(prior parent_id, 8) not in (0, 7)) or
(id = prior parent_id - 6 and mod(prior parent_id, 8) not in (0, 7)) or
(id = prior parent_id + 17 and mod(prior parent_id, 8) not in (0)) or
(id = prior parent_id - 15 and mod(prior parent_id, 8) not in (0)) or
(id = prior parent_id - 10 and mod(prior parent_id, 8) not in (1, 2))or
(id = prior parent_id + 6 and mod(prior parent_id, 8) not in (1, 2)) or
(id = prior parent_id - 17 and mod(prior parent_id, 8) not in (1)) or
(id = prior parent_id + 15 and mod(prior parent_id, 8) not in (1))
)
)
start with s_name = 'c4'
)
where lvl = 64 and rownum = 1;