A semi-prime is a positive integer that has only 2 and exactly 2 prime factors. Here is a list of the first few semi-primes:
.
. We define a Semi-prime Leap Year Pair as a pair of years, whose difference is a semi-prime number and at least one year in the pair is a leap year. Examples of semi-prime leap year pairs are: 
, 
, and 
.
, , and .Given a year number y, write a program that counts the number of semi-prime leap year pairs between year 
and y, inclusive.
and y, inclusive.NOTE: Leap years are defined as those years that are divisible by 4, except for those that ends in 
, in which case a year is a leap year only if it is divisible by 
. This rule was introduced only starting 
. Before , the rule is much simpler, namely, except for 
, all years that are multiples of 4, are leap years. Please apply the appropriate rule for each year. Also, please assume that there will not be any more leap year definition changes in the future.
, in which case a year is a leap year only if it is divisible by . This rule was introduced only starting . Before , the rule is much simpler, namely, except for , all years that are multiples of 4, are leap years. Please apply the appropriate rule for each year. Also, please assume that there will not be any more leap year definition changes in the future.EXAMPLE: For 
, the semi-primes are: 
, and the leap years are: 
. Therefore the semi-prime leap year pairs for this case are as follows:
, the semi-primes are: , and the leap years are: . Therefore the semi-prime leap year pairs for this case are as follows:
Therefore, in this case the function should return: 
pairs.
pairs.Solution Stats
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I scored it medium because even though it took way more time than it should have, I didn't do any literature searches.
OBTW, the drop from my first to second solution was due to borrowing @Tim 's semiprime generator, which I shall likely also use on ES 47, Boxes with Prime Edges.