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A014575
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Vampire numbers (definition 2): numbers n with an even number of digits which have a factorization n = i*j where length(i) = length(j) = length(n)/2 and the multiset of the digits of n coincides with the multiset of the digits of i and j.
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14
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1260, 1395, 1435, 1530, 1827, 2187, 6880, 102510, 104260, 105210, 105264, 105750, 108135, 110758, 115672, 116725, 117067, 118440, 120600, 123354, 124483, 125248, 125433, 125460, 125500, 126027, 126846, 129640
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| The numbers i and j may not both have trailing zeros. Numbers may have more than one such factorization. However, each n is listed only once. [Comment modified by Rick L. Shepherd (rshepherd2(AT)hotmail.com), Nov 02 2009]
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REFERENCES
| C. A. Pickover, "Vampire Numbers." Ch. 30 in Keys to Infinity. New York: Wiley, pp. 227-231, 1995.
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LINKS
| Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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EXAMPLE
| 1260 = 21*60, 1395 = 15*93, 1435 = 35*41, 1530 = 30*51, etc.
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CROSSREFS
| The following sequences are all closely related: A020342, A014575, A080718, A048936, A144563.
Cf. A048933, A048934, ..., A048939.
Sequence in context: A159726 A048130 A099592 * A144563 A175746 A179690
Adjacent sequences: A014572 A014573 A014574 * A014576 A014577 A014578
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KEYWORD
| nonn,base
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AUTHOR
| Eric Weisstein (eric(AT)weisstein.com)
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EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), Jan 03 2009
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