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 1-3 of 3 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

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

A118992 Number of real n X n invertible symmetric (+1,-1) matrices.

Original entry on oeis.org

2, 4, 32, 512, 16896, 1190144, 163899904, 46195853312, 25585116626944, 28281621931343872
Offset: 1

Views

Author

Giovanni Resta, May 08 2006

Keywords

Crossrefs

Cf. A056990, A086899, A056989, A118990, A118993, A118994, A118997.

Formula

a(n) = 2^(n*(n+1)/2) - A118990(n) = A118994(n) + A118997(n). - Max Alekseyev, Jun 12 2025

Extensions

a(8)-a(10) from Max Alekseyev, Jun 17 2025
Showing 1-3 of 3 results.

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

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