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.

A054894 a(n+1) = 4*a(n) + 4*a(n-1) - 4*a(n-2) - a(n-3) with a(1)=1, a(2)=2, a(3)=11, a(4)=48.

Original entry on oeis.org

1, 2, 11, 48, 227, 1054, 4921, 22944, 107017, 499106, 2327795, 10856592, 50634107, 236152510, 1101392305, 5136786240, 23957470033, 111735303362, 521122556315, 2430464772336, 11335450631123, 52867436085214, 246568565219689, 1149971737922784, 5363356017597913, 25014169325118818
Offset: 1

Views

Author

Barry Cipra, Jul 04 2000

Keywords

Crossrefs

Column 3 of A332862 (apart from the initial term 1 here).

Programs

  • GAP
    a:=[1,2,11,48];; for n in [5..40] do a[n]:=4*(a[n-1]+a[n-2]-a[n-3]) -a[n-4]; od; a; # G. C. Greubel, Dec 29 2019
  • Magma
    R:=PowerSeriesRing(Integers(), 40); Coefficients(R!( x*(1-2*x-x^2)/(1-4*x-4*x^2+4*x^3+x^4) )); // G. C. Greubel, Dec 29 2019
    
  • Maple
    seq(coeff(series(x^4/((1+2*x)*(2*x^3+x^2-2*x+1)), x, n+1), x, n), n = 0..40); # G. C. Greubel, Dec 29 2019
  • Mathematica
    CoefficientList[Series[(1-2*x-x^2)/(1-4*x-4*x^2+4*x^3+x^4), {x, 0, 40}], x] (* Vincenzo Librandi, May 05 2013 *)
    LinearRecurrence[{4,4,-4,-1},{1,2,11,48},40] (* Harvey P. Dale, May 28 2014 *)
  • PARI
    my(x='x+O('x^66)); Vec(x*(1-2*x-x^2)/(1-4*x-4*x^2+4*x^3+x^4)) \\ Joerg Arndt, May 06 2013
    
  • Sage
    def A054894_list(prec):
        P. = PowerSeriesRing(ZZ, prec)
        return P( x*(1-2*x-x^2)/(1-4*x-4*x^2+4*x^3+x^4) ).list()
    a=A054894_list(40); a[1:] # G. C. Greubel, Dec 29 2019
    

Formula

a(n) = Sum_{k=1..n} Fibonacci(k)^3*a(n-k), with a(0)=1. - Vladeta Jovovic, Apr 23 2003
G.f.: x*(1-2*x-x^2)/(1-4*x-4*x^2+4*x^3+x^4). - Vaclav Kotesovec, Nov 27 2012

A329707 Number of placements of zero or more dominoes on a 2 X n grid where no two empty squares are horizontally adjacent.

Original entry on oeis.org

1, 2, 4, 11, 25, 61, 146, 351, 844, 2028, 4875, 11717, 28163, 67692, 162703, 391070, 939968, 2259289, 5430383, 13052363, 31372406, 75406105, 181244648, 435636112, 1047086489, 2516756727, 6049227537, 14539805696, 34947594281, 83999358146, 201899224084, 485281049587, 1166412095721
Offset: 0

Views

Author

Andrew Howroyd, Feb 28 2020

Keywords

Crossrefs

Row 2 of A332862.

Programs

  • Mathematica
    LinearRecurrence[{2, 1, 0, 0, 0, -1}, {1, 2, 4, 11, 25, 61}, 50] (* Paolo Xausa, Jun 19 2024 *)
  • PARI
    Vec((1 - x)*(1 + x + x^3)/(1 - 2*x - x^2 + x^6) + O(x^30))

Formula

a(n) = 2*a(n-1) + a(n-2) - a(n-6) for n > 6.
G.f.: (1 - x)*(1 + x + x^3)/(1 - 2*x - x^2 + x^6).

A332865 Number of placements of zero or more dominoes on the n X n grid where no two empty squares are horizontally adjacent.

Original entry on oeis.org

1, 4, 48, 1427, 140555, 40008789, 33656587715, 84588476099284, 626461671945179295, 13776144517953719025396, 897220763259635483826935324, 173109540246969825014223808529273, 98978509126162805673620043358494745638, 167661422725328648892707605323564506782035252
Offset: 1

Views

Author

Neil A. McKay, Feb 27 2020

Keywords

Comments

The number of positions of n X n Domineering where horizontal (Right) has no moves, also called Right ends. Domineering is a game in which players take turns placing dominoes on a grid, one player placing vertically and the other horizontally until the player to place cannot place a domino.

Crossrefs

Main diagonal of A332862.
Cf. A287595 (the number of placements of dominoes on an n X n grid where no two empty squares are horizontally or vertically adjacent).
Cf. A332714.

Programs

  • Sage
    # See Bjorn Huntemann, Svenja Huntemann, Neil A. McKay link.

Extensions

a(9)-a(14) from Andrew Howroyd, Feb 28 2020
Showing 1-3 of 3 results.