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 1-6 of 6 results.

A118993 Number of real n X n symmetric (+1,-1) matrices with nonzero permanent.

Original entry on oeis.org

2, 4, 64, 832, 23808, 1725952, 268435456, 64638447616, 33770336417792
Offset: 1

Views

Author

Giovanni Resta, May 08 2006

Keywords

Crossrefs

Cf. A086899, A118988, A118991, A118992, A118995, A118999, A119001, A119010.

Extensions

a(8)-a(9) from Max Alekseyev, Jun 18 2025

A118995 Number of real n X n symmetric (+1,-1) matrices with positive permanent.

Original entry on oeis.org

1, 4, 32, 592, 11904, 1192384, 134217728, 41896879104, 16885168208896
Offset: 1

Views

Author

Giovanni Resta, May 08 2006

Keywords

Crossrefs

Cf. A086900, A118988, A118999, A118993, A118994, A118999, A119001, A119010.

Formula

a(n) = A118993(n) - A118999(n). For odd n, a(n) = A118999(n) = A118993(n)/2. - Max Alekseyev, Jun 18 2025

Extensions

a(8)-a(9) from Max Alekseyev, Jun 18 2025

A119001 Minimal permanent of real n X n symmetric (+1,-1) matrices.

Original entry on oeis.org

-1, 0, -6, -8, -120, -96, -5040, -4320, -362880
Offset: 1

Views

Author

Giovanni Resta, May 08 2006

Keywords

Crossrefs

Cf. A118988, A118993, A118995, A118999, A119000, A119010.

Formula

For odd n, a(n) = -n!. - Max Alekseyev, Jun 18 2025

A119010 Number of symmetric n X n (+1,-1)-matrices over the reals with zero permanent.

Original entry on oeis.org

0, 4, 0, 192, 8960, 371200, 0, 4081029120, 1414035671040
Offset: 1

Views

Author

Giovanni Resta, May 08 2006

Keywords

Crossrefs

Cf. A086906, A088672, A118988, A118989, A118990, A118993, A118995, A118999, A119001.

Extensions

a(8)-a(9) from Max Alekseyev, Jun 18 2025

A118996 Number of real n X n symmetric (0,1) matrices with negative determinant.

Original entry on oeis.org

0, 3, 27, 190, 4410, 753592, 127793708, 21893984392, 9100020369720, 16451259308386616
Offset: 1

Views

Author

Giovanni Resta, May 08 2006

Keywords

Crossrefs

Cf. A086899, A086900, A086906, A118997, A118998, A118999, A119006.

Formula

a(n) = A086899(n) - A086900(n) = 2^(n*(n+1)/2) - A086906(n) - A086900(n). - Max Alekseyev, Jun 12 2025

Extensions

a(8)-a(10) from Max Alekseyev, Jun 17 2025

A118997 Number of real n X n symmetric (+1,-1) matrices with negative determinant.

Original entry on oeis.org

1, 4, 16, 80, 8448, 907904, 81949952, 13480664064, 12792558313472, 18963201072750592
Offset: 1

Views

Author

Giovanni Resta, May 08 2006

Keywords

Crossrefs

Cf. A118999, A118992, A118994, A118996, A119000.

Formula

a(2n+1) = A118994(2n+1) = A118992(2n+1)/2. - Max Alekseyev, May 08 2009
a(n) = A118992(n) - A118994(n). - Max Alekseyev, Jun 12 2025

Extensions

a(8)-a(10) from Max Alekseyev, Jun 17 2025
Showing 1-6 of 6 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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