cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

A359296 Absolute discriminants of imaginary quadratic fields with elementary bicyclic 7-class group and capitulation type the identity permutation.

Original entry on oeis.org

4973316, 5073691
Offset: 1

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Keywords

Comments

An algebraic number field with this capitulation type has a 7-class field tower of precise length 2 with Galois group isomorphic to the Schur sigma-group SmallGroup(16807,7). It is a solution to the problem posed by Olga Taussky-Todd in 1970.

Examples

			The second, respectively first, imaginary quadratic field with 7-class group (7,7) and identity capitulation (12345678) has discriminant -5073691, respectively -4973316, and was discovered by Daniel C. Mayer on 26 October 2019, respectively 09 November 2019. It has ordinal number 555, respectively 545, in the sequence of all imaginary quadratic fields with 7-class group (7,7).
		

Crossrefs

Cf. A359291.

A359871 Absolute discriminants of imaginary quadratic number fields with elementary bicyclic 5-class group (5,5).

Original entry on oeis.org

11199, 12451, 17944, 30263, 33531, 37363, 38047, 39947, 42871, 53079, 54211, 58424, 61556, 62632, 63411, 64103, 65784, 66328, 67031, 67063, 67128, 69811, 72084, 74051, 75688, 83767, 84271, 85099, 85279, 87971, 89751, 90795, 90868, 92263, 98591, 99031, 99743
Offset: 1

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Author

Keywords

Comments

The maximal unramified pro-5-extension, that is, the Hilbert 5-class field tower, of these imaginary quadratic fields must have a Schur sigma-group as its Galois group. The tower has an unbounded number of stages at least equal to two, and may even be infinite.

Examples

			On page 22 of their 1982 paper, Franz-Peter Heider and Bodo Schmithals gave the smallest prime discriminant -12451 and determined two of the six capitulation kernels in unramified cyclic quintic extensions. On 03 November 2011, Daniel C. Mayer determined the abelian type invariants, and thus indirectly the coarse capitulation type, of these six extensions for all 37 discriminants in the range between -11199 and -99743, with computational aid by Claus Fieker. In particular, -89751 was the minimal occurrence of the identity capitulation (see A359291). In his 2012 Ph.D. thesis, Tobias Bembom independently recomputed the capitulation in this range, without being able to detect the identity capitulation for -89751. It must be pointed out that in his table on pages 129 and 130, the minimal discriminant -11199=-3*3733 is missing, whereas the discriminant -81287 is superfluous and must be cancelled, since its 5-class group is non-elementary bicyclic of type (25,5).
		

References

  • F.-P. Heider, B. Schmithals, Zur Kapitulation der Idealklassen in unverzweigten primzyklischen Erweiterungen, J. reine angew. Math. 336 (1982), 1 - 25.
  • D. C. Mayer, The distribution of second p-class groups on coclass graphs, J. Théor. Nombres Bordeaux 25 (2013), no. 2, 401-456. (Sec. 3.5.2, p. 448)

Crossrefs

Cf. A359291 (subsequence), A242863 (3,3), A359872 (7,7).

Programs

  • 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 ([5,5] eq pPrimaryInvariants(C,5)) then d, ", "; end if; end if; end for;
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