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A242862
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Absolute discriminants of complex quadratic fields with 3-class rank 2.
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15
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3299, 3896, 4027, 5703, 6583, 8751, 9748, 10015, 11651, 12067, 12131, 15544, 16627, 17131, 17399, 17723, 18555, 19187, 19427, 19651, 19679, 19919, 20276, 20568, 21224, 21668, 22395, 22443, 22711, 23428, 23683
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OFFSET
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1,1
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COMMENTS
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The length of the Hilbert 3-class field tower of a complex quadratic field is infinite for 3-class rank at least 3, and it is 1 for 3-class rank 1. In contrast, the length is at least 2 but unbounded for 3-class rank 2, whence this is the only unsolved interesting case.
The terms 3299, 4027 and 9748 have been discussed in detail by Scholz and Taussky. In a footnote they also mention 3896 with an erroneous claim.
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REFERENCES
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H. Koch, B. B. Venkov, Über den p-Klassenkörperturm eines imaginär-quadratischen Zahlkörpers, Astérisque 24-25 (1975), 57-67.
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LINKS
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EXAMPLE
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For n=1,4, resp. n=2,3, the 3-class group is of type (3,9), resp. (3,3).
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PROG
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(Magma)
for d := 2 to 10^5 do a := false; if (3 eq d mod 4) and IsSquarefree(d) then a := true; end if; if (0 eq d mod 4) then r := d div 4; if IsSquarefree(r) and ((2 eq r mod 4) or (1 eq r mod 4)) then a := true; end if; end if; if (true eq a) then K := QuadraticField(-d); C := ClassGroup(K); if (2 eq #pPrimaryInvariants(C, 3)) then d, ", "; end if; end if; end for;
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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