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CREATE OR REPLACE FUNCTION f_stealth( needle int )
RETURNS int
AS $CODE$
WITH numbers AS ( SELECT generate_series( 2, needle ) as n )
, pairs AS (
SELECT needle as n
, n as divisor
, needle / n as divisor_2
, case needle % n
when 0 then n + needle / n
else null
end as summix
from numbers
)
, stealth as (
select *
, abs( summix - lag( summix, 1, summix ) over ( ORDER BY summix DESC ) ) as lag
, abs( summix - lead( summix, 1, summix ) over ( ORDER BY summix DESC ) ) as lead
FROM pairs
where summix is not null
)
SELECT CASE count(*)
WHEN 0 THEN 0
ELSE 1
END
FROM stealth
WHERE ( lag = 1 or lead = 1 );
$CODE$
LANGUAGE sql;
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