OraQA

The following is an interesting puzzle posted on MathPuzzles:

I had great difficulty trying to remember my social security identity number, a long string of digits, until I realized that it is the largest number in which every block of two adjacent digits is a different prime or square number. What number is it?

—————————SQL Solution———————————-

SELECT
max(to_number(replace(sys_connect_by_path(
                      CASE LEVEL
                           WHEN 1 THEN to_char(num)
                           ELSE second
                       END,','),','))) as SSN#
FROM
(SELECT num, substr(num,1,1) first, substr(num,2,1) second
 FROM
 (SELECT num
  FROM
  (WITH data AS (SELECT LEVEL+1 num FROM dual CONNECT BY LEVEL <=100)
   SELECT num FROM data WHERE num <= 100
   MINUS
   SELECT  d1.num * d2.num
   FROM data d1, data d2
   WHERE  d1.num <= d2.num
   AND d1.num <= sqrt(100)
  )
  WHERE num >=10
  UNION
  SELECT power(LEVEL,2) num from dual WHERE power(LEVEL,2) >=10
  CONNECT BY LEVEL <=9
 )
)
WHERE LEVEL = 8
CONNECT BY NOCYCLE PRIOR first != second
AND PRIOR second = first
AND LEVEL <=8;
      SSN#
---------------------
 973671649

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