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 1-2 of 2 results.

A244521 Number of pseudo-square parallelogram (psp) polyominoes by semiperimeter.

Original entry on oeis.org

1, 2, 3, 6, 11, 22, 45, 90, 184, 370, 751, 1516, 3053, 6172, 12405, 25042, 50323, 101424, 203880, 410296, 824871, 1658338, 3333405, 6696814, 13457112, 27021758, 54278993, 108952646, 218765704, 439001338, 881134467
Offset: 2

Views

Author

Joerg Arndt, Jul 20 2014

Keywords

Comments

Terms taken from p. 13 of the Brlek et al. reference.

Links

Crossrefs

Cf. A245185.

Extensions

a(29)-a(32) from Andrew Howroyd, Mar 01 2020

A245437 Expansion of x^5/(x^6-x^4-x^2-x+1).

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 1, 2, 3, 6, 10, 17, 29, 50, 86, 147, 252, 432, 741, 1270, 2177, 3732, 6398, 10968, 18802, 32232, 55255, 94723, 162382, 278369, 477204, 818064, 1402395, 2404105, 4121322, 7065122, 12111635, 20762798, 35593360, 61017175, 104600848, 179315699
Offset: 0

Views

Author

Vincenzo Librandi, Jul 22 2014

Keywords

Comments

G.f. taken from p. 12 of the Brlek et al. reference.

Links

Crossrefs

Cf. A079500, A175331, A244521, A245185.

Programs

  • Magma
    [n le 6 select Floor(n/6) else Self(n-1)+Self(n-2)+Self(n-4)-Self(n-6): n in [1..50]];
  • Mathematica
    CoefficientList[Series[x^5/(x^6 - x^4 - x^2 - x + 1), {x, 0, 50}], x]
LinearRecurrence[{1, 1, 0, 1, 0, -1}, {0, 0, 0, 0, 0, 1}, 50] (* Bruno Berselli, Jul 22 2014 *)

Formula

G.f.: x^5/(x^6 - x^4 - x^2 - x + 1).
a(n) = a(n-1) + a(n-2) + a(n-4) - a(n-6) for n>5.
Showing 1-2 of 2 results.

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

Content is available under The OEIS End-User License Agreement.