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Vampire Number
A number v=xy with an even number n of digits formed by multiplying a pair of n/2-digit numbers (where the digits are taken from the original number in any order) x and y together. Pairs of trailing zeros are not allowed. If v is a vampire number, then x and y are called its "fangs." Examples of vampire numbers include 1260 = 21·60 (1) 1395 = 15·93 (2) 1435 = 35·41 (3) 1530 = 30·51 (4) 1827 = 21·87 (5) 2187 = 27·81 (6) 6880 = 80·86 (7) ...
Vampire numbers having two distinct pairs of fangs include Vampire numbers having three distinct pairs of fangs include General formulas can be constructed for special classes of vampires, such as the fangs
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