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.

A002106 Number of transitive permutation groups of degree n.

Original entry on oeis.org

1, 1, 2, 5, 5, 16, 7, 50, 34, 45, 8, 301, 9, 63, 104, 1954, 10, 983, 8, 1117, 164, 59, 7, 25000, 211, 96, 2392, 1854, 8, 5712, 12, 2801324, 162, 115, 407, 121279, 11, 76, 306, 315842, 10, 9491, 10, 2113, 10923, 56, 6
Offset: 1

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Comments

It is conjectured that this is the number of Galois groups for irreducible polynomials of order n. (All such Galois groups are transitive.) - Charles R Greathouse IV, May 28 2014
Let G be a transitive permutation groups of degree n. Then G occurs as a Galois group for an irreducible polynomial of degree n with coefficients K if and only if K admits a Galois extension with Galois group G. ("=>" is true by definition of the Galois group for an irreducible polynomial; for "<=", see user631's answer in the Math Overflow link). Hence the conjecture above is equivalent to the inverse Galois problem. Every finite group can be realized as a Galois group of some extension L/K, but for a fixed base field K (for example, K = Q is the field of rational numbers) the question is usually open. - Jianing Song, May 26 2025

Examples

			a(3)=2: A_3 and S_3.
		

References

  • G. Butler and J. McKay, personal communication.
  • C. C. Sims, Computational methods in the study of permutation groups, pp. 169-183 of J. Leech, editor, Computational Problems in Abstract Algebra. Pergamon, Oxford, 1970.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • GAP
    a:=function(n)
    return Length(AllTransitiveGroups(NrMovedPoints,n));
    end; # Charles R Greathouse IV, May 28 2014

Extensions

Corrected and extended to degree 31 by Alexander Hulpke, Aug 15 1996
Further corrections from Alexander Hulpke, Feb 19 2002
Degree 32 extended by Artur Jasinski, Feb 17 2011
Extended to degree 47 by Gabriel Verret, May 07 2016