

A048937


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}.


2



13078260, 107650322640, 113024597400, 119634515208, 134549287600, 135173486250, 138130447950, 146083269717, 150967233648, 216315684000, 221089445500, 315987404670, 463997983680, 472812953760, 10174695862032, 10178463985200, 10185571893960, 10476754939728, 10624657891320
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OFFSET

1,1


COMMENTS

f_{n/2} and g_{n/2} may not both be zero.
Vampire numbers (definition 2) having exactly three distinct pairs of fangs.


REFERENCES

C. A. Pickover, "Vampire Numbers." Ch. 30 in Keys to Infinity. New York: Wiley, pp. 227231, 1995.


LINKS



EXAMPLE

13078260 = 1620*8073 = 1863*7020 = 2070*6318; 107650322640 = 153204*702660 = 140532*766020 = 200760*536214.


CROSSREFS



KEYWORD

nonn,base


AUTHOR



EXTENSIONS

More terms found by Walter Schneider, Feb 11 2002 and communicated by Hans Havermann, Oct 10 2002


STATUS

approved



