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.

A086442 a(n) = A086323(n)/n.

Original entry on oeis.org

1, 1, 2, 2, 6, 6, 18, 20, 50, 74, 186, 216, 630, 916, 2002, 3040, 7710, 10806, 27594, 40642, 94658, 158492, 364722, 516682, 1333926, 2180772, 4770374, 7845774, 18512790, 28706044, 69273666, 111116576, 251853466, 436650938, 977895330
Offset: 1

Views

Author

Vladeta Jovovic, Sep 09 2003

Keywords

Crossrefs

Cf. A086323.

Extensions

More terms from Max Alekseyev, Sep 25 2009

A086328 Number of n X n circulant singular (0,1) matrices over the reals.

Original entry on oeis.org

1, 2, 2, 8, 2, 28, 2, 96, 62, 284, 2, 1504, 2, 3560, 2738, 16896, 2, 67636, 2, 235736, 109334, 707480, 2, 4376848, 206282, 10408792, 5417630, 48753784, 2, 212560504, 2, 739236864, 278770214, 2333737292, 133401818, 13837799440, 2
Offset: 1

Views

Author

Yuval Dekel (dekelyuval(AT)hotmail.com), Aug 30 2003

Keywords

Comments

a(2*n+1) = A144926(2*n+1), n>0. a(2*p) = 2^p + binomial(2*p,p) if p is an odd prime, cf. A144926. - Vladeta Jovovic, Oct 02 2008

Links

Crossrefs

Cf. A086323, A086324.

Formula

a(n) = 2^n - A086323(n).
For a prime p, a(p) = 2 and the two circulants are those with all rows equal (0, 0, 0, ..., 0) or all rows equal (1, 1, 1, ..., 1).

Extensions

More terms from Fred Lunnon, Oct 28 2008
a(0) removed, a(1) corrected by Max Alekseyev, Sep 25 2009

A086432 Maximum of |det(A)| where A is an n X n circulant (0,1) matrix over the integers.

Original entry on oeis.org

1, 1, 2, 3, 4, 9, 32, 45, 95, 275, 1458, 2240, 6561, 19952, 131072, 214245, 755829, 2994003, 19531250, 37579575, 134534444, 577397064, 4353564672, 10757577600, 31495183733, 154611524732, 738139162166, 3124126889325, 11937232425585, 65455857159975
Offset: 1

Views

Author

Yuval Dekel (dekelyuval(AT)hotmail.com), Sep 08 2003

Keywords

Links

Crossrefs

Cf. A086323.
Cf. A215723 (same for circulant (+1,-1) matrices), A215724 (same for (1,-1)-Toeplitz matrices).

Programs

  • Mathematica
    Do[m=0;j=i-1;n=k=2^j; Do[l=IntegerDigits[k,2]; m=Max[m,Det[NestList[RotateRight,l,j]]]; k++,{n}]; Print[m], {i,30}] (* Hans Havermann, Dec 05 2012 *)

Extensions

More terms from Vladeta Jovovic, Sep 09 2003
a(19)-a(22) from Joerg Arndt, Aug 25 2012
a(23)-a(30) from Hans Havermann, Dec 05 2012

A086479 Number of invertible circulant (0,1) matrices over the reals that have even determinant.

Original entry on oeis.org

0, 0, 3, 0, 15, 12, 77, 32, 261, 260, 1023, 1056, 4095, 6552, 19905, 15872, 66045, 97740, 262143, 321320, 1404375, 1391720, 4198397, 6108912, 17619525, 23153832, 79255071, 116921224, 268435455, 529405320, 1259979965, 1408246784
Offset: 1

Views

Author

Yuval Dekel (dekelyuval(AT)hotmail.com), Sep 09 2003

Keywords

Crossrefs

Cf. A003473, A086323, A086324.

Formula

a(n) = A086323(n) - A003473(n)

Extensions

More terms from Max Alekseyev, Sep 25 2009
Showing 1-4 of 4 results.

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