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.

A030129 Number of nonisomorphic Steiner triple systems (STS's) S(2,3,n) on n points.

Original entry on oeis.org

1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 2, 0, 80, 0, 0, 0, 11084874829, 0, 14796207517873771
Offset: 1

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Comments

a(n) also counts the following objects:
isomorphism classes of idempotent totally symmetric Latin squares of order n,
isotopism classes containing idempotent totally symmetric Latin squares of order n,
species containing idempotent totally symmetric Latin squares of order n,
isomorphism classes of totally symmetric loops of order n+1,
isomorphism classes of totally symmetric unipotent Latin squares of order n+1,
isomorphism classes containing totally symmetric reduced Latin squares of order n+1,
isotopism classes containing totally symmetric unipotent Latin squares of order n+1,
isotopism classes containing totally symmetric reduced Latin squares of order n+1,
species containing totally symmetric unipotent Latin squares of order n+1, and
species containing totally symmetric reduced Latin squares of order n+1.

References

  • L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 304.
  • CRC Handbook of Combinatorial Designs, 1996, p. 70.

Crossrefs

A051390 Number of nonisomorphic Steiner quadruple systems (SQS's) of order n.

Original entry on oeis.org

1, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 4, 0, 1054163
Offset: 1

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Keywords

Examples

			There are 4 nonisomorphic SQS's on 14 points.
		

References

  • CRC Handbook of Combinatorial Designs, 1996, circa p. 70.
  • A. Hartman and K. T. Phelps, Steiner quadruple systems, pp. 205-240 of Contemporary Design Theory, ed. Jeffrey H. Dinitz and D. R. Stinson, Wiley, 1992.

Crossrefs

See A124120, A124119 for other versions of this sequence. The present entry is the official version.

Formula

a(n) = 0 unless n = 1 or n == 2 or 4 (mod 6).

A124120 Number of nonisomorphic Steiner quadruple systems (SQS's) S(3,4,n) on n points.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 4, 0, 1054163
Offset: 1

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Author

N. J. A. Sloane, Nov 30 2006

Keywords

Examples

			There are 4 nonisomorphic SQS's on 14 points.
		

Crossrefs

A051390 is the official version of this sequence and has all the references etc.

A051391 Number of nonisomorphic Steiner triple systems (STS's) S(2,3,v) on v = 6n+1 or 6n+3 points.

Original entry on oeis.org

1, 1, 1, 1, 2, 80, 11084874829
Offset: 1

Views

Author

Keywords

Examples

			There are 2 nonisomorphic STS's on 13 points.
		

References

  • L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 304.
  • CRC Handbook of Combinatorial Designs, 1996, p. 70.

Crossrefs

Showing 1-4 of 4 results.