Vampire Number
Vampire numbers are even-digit numbers expressible as products of two fangs with rearranged digits, prohibiting both fangs from ending in zero. Pseudovampire numbers have multiplicands of different digit counts.
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A vampire number is defined as a number with an even number of digits that can be expressed as the product of two numbers, known as "fangs," which must also have the same number of digits. The digits of the fangs must be a rearrangement of the digits of the vampire number, and they cannot both end in zero. Examples of vampire numbers include various 8-digit and 10-digit numbers, with specific sequences cataloged in the On-Line Encyclopedia of Integer Sequences (OEIS). The study of vampire numbers also includes those with distinct pairs of fangs, with some having up to five pairs. Additionally, there are pseudovampire numbers where the multiplicands have different digit counts. General formulas exist for certain classes of vampire numbers, and the concept has been explored in various mathematical literature.
- Vampire numbers are formed by multiplying two numbers with the same number of digits.
- The digits of the fangs must be a rearrangement of the digits of the vampire number.
- Pairs of trailing zeros in the fangs are not allowed.
- There are specific sequences of vampire numbers documented in OEIS.
- Pseudovampire numbers exist, where the multiplicands have different digit counts.
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5 commentsthe fundamental arithmetic theorem would have me re-express all those numbers as the product of primes that they actually are.
I find pairing this list of primes (with powers) and splitting them into two groups to be ultimately arbitrary which blinds me from the significance of these 'kind' of numbers
i.e. i'm saying 'vampire numbers' are a lame kind of number because it involves arbitrary choices which are IMO stinky; they lack exactlyness
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