Variants
Pseudovampire numbers are similar to vampire numbers, except that the fangs of an n-digit pseudovampire number need not be of length n/2 digits. Pseudovampire numbers can have an odd number of digits, for example 126 = 6×21.
More generally, you can allow more than two fangs. In this case, vampire numbers are numbers n which can be factorized using the digits of n. For example, 1395 = 5×9×31. This sequence starts (sequence A020342 in OEIS):
- 126, 153, 688, 1206, 1255, 1260, 1395, ...
A prime vampire number, as defined by Carlos Rivera in 2002, is a true vampire number whose fangs are its prime factors. The first few prime vampire numbers are:
- 117067, 124483, 146137, 371893, 536539
As of 2006 the largest known is the square (94892254795×1045418+1)2, found by Jens K. Andersen in 2002.
Read more about this topic: Vampire Number
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