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Search: id:A048937
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| A048937 |
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Numbers n with an even number of digits, n = d_1 d_2 ... d_n, such that there are exactly three ways to partition the digits into two groups of size n/2, say f_1 ... f_{n/2} and g_1 ... g_{n/2}, such that n = f_1 ... f_{n/2} * g_1 ... g_{n/2}. |
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2
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| 13078260, 107650322640, 113024597400, 119634515208, 134549287600, 135173486250, 138130447950, 146083269717, 150967233648, 216315684000, 221089445500, 315987404670, 463997983680, 472812953760, 10174695862032, 10178463985200, 10185571893960, 10476754939728, 10624657891320
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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f_{n/2} and g_{n/2} may not both be zero.
Vampire numbers having exactly three distinct pairs of fangs.
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REFERENCES
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C. A. Pickover, "Vampire Numbers." Ch. 30 in Keys to Infinity. New York: Wiley, pp. 227-231, 1995.
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LINKS
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Walter Schneider, Vampire numbers
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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EXAMPLE
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13078260 = 1620*8073 = 1863*7020 = 2070*6318; 107650322640 = 153204*702660 = 140532*766020 = 200760*536214.
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CROSSREFS
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Cf. A014575, A048933, ..., A048939.
Sequence in context: A070189 A102335 A083405 this_sequence A094801 A015425 A126724
Adjacent sequences: A048934 A048935 A048936 this_sequence A048938 A048939 A048940
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KEYWORD
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nonn,base
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AUTHOR
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Eric Weisstein (eric(AT)weisstein.com)
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EXTENSIONS
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More terms found by Walter Schneider, Feb 11, 2002 and communicated by Hans Havermann, Oct 10, 2002
More terms from Jens Kruse Andersen (jens.k.a(AT)get2net.dk), Dec 01 2002
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