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 1-4 of 4 results.

A004029 Number of n-dimensional space groups.

Original entry on oeis.org

1, 2, 17, 219, 4783, 222018, 28927915
Offset: 0

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Author

Keywords

Comments

Right border of A293060. - Andrey Zabolotskiy, Oct 07 2017

References

  • H. Brown, R. Bülow, J. Neubüser, H. Wondratschek and H. Zassenhaus, Crystallographic Groups of Four-Dimensional Space. Wiley, NY, 1978, p. 52.
  • P. Engel, Geometric crystallography, in P. M. Gruber and J. M. Wills, editors, Handbook of Convex Geometry. North-Holland, Amsterdam, Vol. B, pp. 989-1041.
  • J. E. Goodman and J. O'Rourke, editors, Handbook of Discrete and Computational Geometry, CRC Press, 1997, p. 102 and 934.
  • T. Janssen, Crystallographic Groups. North-Holland, Amsterdam, 1973, p. 119.
  • R. L. E. Schwarzenberger, N-Dimensional Crystallography. Pitman, London, 1980, p. 34.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Extensions

a(6) corrected by W. Plesken and T. Schulz. Thanks to Max Horn for reporting this correction, Dec 18 2009

A293061 Triangle read by rows (n >= 0, 0 <= k <= n): T(n,k) = number of k-dimensional subperiodic groups in n-dimensional space, counting enantiomorphs.

Original entry on oeis.org

1, 2, 2, 10, 7, 17, 32, 75, 80, 230, 271, 343, 1091, 1594, 4894, 955
Offset: 0

Views

Author

Andrey Zabolotskiy, Sep 29 2017

Keywords

Comments

T(n,0) count n-dimensional crystallographic point groups, T(n,n) count n-dimensional space groups (i.e., right border is A006227). The name "subperiodic groups" is usually related to the case 0 < k < n only, i.e., symmetry groups of n-dimensional objects including k independent translations which are subgroups of some n-dimensional space groups.
The Bohm symbols for these groups are G_{n,k}, except for the case k=n, when it is G_n.
Some groups have their own names:
T(2,1): frieze groups
T(2,2): wallpaper groups
T(3,1): rod groups
T(3,2): layer groups
[Palistrant, 2012, p. 476] gives correct T(4,k), k=0,1,2,3 but incorrect T(4,4). For correct value of T(4,4), see [Souvignier, 2006, p. 80].

Examples

			The triangle begins:
    1;
    2,   2;
   10,   7,   17;
   32,  75,   80,  230;
  271, 343, 1091, 1594, 4894;
  955, ...
		

Crossrefs

A293062 Triangle read by rows (n >= 0, 0 <= k <= n): T(n,k) = number of k-dimensional magnetic subperiodic groups in n-dimensional space, not counting enantiomorphs.

Original entry on oeis.org

2, 5, 7, 31, 31, 80, 122, 360, 528, 1594, 1025
Offset: 0

Views

Author

Andrey Zabolotskiy, Sep 29 2017

Keywords

Comments

Magnetic groups are also known as antisymmetry groups, or black-white, or two-color crystallographic groups.
T(n,0) count n-dimensional magnetic crystallographic point groups, T(n,n) count n-dimensional magnetic space groups. The name "subperiodic groups" is usually related to the case 0 < k < n only, i.e., magnetic groups of n-dimensional objects including k independent translations which are subgroups of some n-dimensional magnetic space groups.
The Bohm-Koptsik symbols for these groups are G_{n,k}^1 (or G_{n+1,n,k}; the difference arises only when we consider enantiomorphism), except for the case k=n, when it is G_n^1 (or G_{n+1,n}).
T(2,1) are band groups.
T(3,3) are Shubnikov groups.
For T(n,0) and T(n,n), see [Souvignier, 2006, table 1]. See Litvin for the cases when there are no enantiomorphs: rows 1-2, T(3,2). For T(3,1), see, e.g., [Palistrant & Jablan, 1991].

Examples

			The triangle begins:
     2;
     5,   7;
    31,  31,  80;
   122, 360, 528, 1594;
  1025, ...
		

Crossrefs

Formula

T(n,n) = A293060(n+1,n).

A293063 Triangle read by rows (n >= 0, 0 <= k <= n): T(n,k) = number of k-dimensional magnetic subperiodic groups in n-dimensional space, counting enantiomorphs.

Original entry on oeis.org

2, 5, 7, 31, 31, 80, 122, 394, 528, 1651, 1202
Offset: 0

Views

Author

Andrey Zabolotskiy, Sep 29 2017

Keywords

Comments

Magnetic groups are also known as antisymmetry groups, or black-white, or two-color crystallographic groups.
T(n,0) count n-dimensional magnetic crystallographic point groups, T(n,n) count n-dimensional magnetic space groups (A307291). The name "subperiodic groups" is usually related to the case 0 < k < n only, i.e., magnetic groups of n-dimensional objects including k independent translations which are subgroups of some n-dimensional magnetic space groups.
The Bohm-Koptsik symbols for these groups are G_{n,k}^1, except for the case k=n, when it is G_n^1.
T(2,1) are band groups.
T(3,3) are Shubnikov groups.
For T(n,0) and T(n,n), see [Souvignier, 2006, table 1]. For rows 1-3, see Litvin.

Examples

			The triangle begins:
     2;
     5,   7;
    31,  31,  80;
   122, 394, 528, 1651;
  1202, ...
		

Crossrefs

Showing 1-4 of 4 results.