Unashamed Primes: Sexy Triplets

A sexy (from sex, the Latin word for six) prime triplet is a group of three primes that differ by each other by 6, with the sum of the smallest prime plus 18 being a composite number.

You must implement a function that returns a list of triplets (triplets being lists in turn) found in a range, which included bounds are the two given integers low and high.

Examples

sexy_triplets(1, 19) ➞ [ [7, 13, 19] ]
# 7 + 6 = 13 + 6 = 19 and 7 + 18 = 25 (composite)

sexy_triplets(5, 17) ➞ []
# Despite [5, 11, 17] can seem a triplet, 5 + 18 = 23 (not composite)

sexy_triplets(64, 88) ➞ [ [67, 73, 79] ]
# 67 + 6 = 73 + 6 = 79 and 67 + 18 = 85 (composite)

Notes

• If no triplets are found in the range, return an empty list (see example #2).
• A composite number is trivially a not prime number.