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 1-7 of 7 results.

A086906 Number of symmetric singular n X n (0,1) matrices over the reals.

Original entry on oeis.org

1, 4, 32, 496, 14172, 816684, 87982904, 18748545824, 7565600671504, 5940152086634096
Offset: 1

Views

Author

Yuval Dekel (dekelyuval(AT)hotmail.com), Sep 19 2003

Keywords

Crossrefs

Cf. A046747, A086899, A086879, A086900, A118989, A118990, A118991, A118996, A119008, A119010.
Cf. A006125.

Formula

a(n) = 2^(n*(n+1)/2) - A086899(n).

Extensions

W. Edwin Clark computed the first entries.
a(6)-a(7) from Giovanni Resta, May 08 2006
a(8)-a(10) from Max Alekseyev, Jun 17 2025

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

A118999 Number of real n X n symmetric (+1,-1) matrices with negative permanent.

Original entry on oeis.org

1, 0, 32, 240, 11904, 533568, 134217728, 22741568512, 16885168208896
Offset: 1

Views

Author

Giovanni Resta, May 08 2006

Keywords

Crossrefs

Cf. A118988, A118997, A118999, A118993, A118994, A118995, A119001, A119010.

Formula

a(n) = A118993(n) - A118995(n). For odd n, a(n) = A118995(n) = A118993(n)/2. - Max Alekseyev, Jun 18 2025

Extensions

a(1) corrected and a(8)-a(9) added by 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

A118989 Number of symmetric n X n (0,1)-matrices over the reals with zero permanent.

Original entry on oeis.org

1, 3, 25, 271, 6881, 254911, 20903681, 2725061631, 771426498049
Offset: 1

Views

Author

Giovanni Resta, May 08 2006

Keywords

Crossrefs

Cf. A086906, A088672, A118986, A118991, A119009, A119010.

Formula

a(n) = 2^(n*(n+1)/2) - A118991(n) = 2^A000217(n) - A118991(n) = A006125(n+1) - A118991(n). - Max Alekseyev, Apr 22 2010; corrected by Herman Jamke (hermanjamke(AT)fastmail.fm), Sep 26 2010

Extensions

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

A118990 Number of symmetric singular n X n (+1,-1) matrices over the reals.

Original entry on oeis.org

0, 4, 32, 512, 15872, 907008, 104535552, 22523623424, 9599255461888, 7747175087620096
Offset: 1

Views

Author

Giovanni Resta, May 08 2006

Keywords

Crossrefs

Cf. A086906, A119010, A057982, A118992.

Formula

a(n) = 2^(n*(n+1)/2) - A118994(n) - A118997(n) = 2^(n*(n+1)/2) - A118992(n). - Max Alekseyev, May 08 2009

Extensions

a(8)-a(10) from Max Alekseyev, Jun 17 2025
Showing 1-7 of 7 results.

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