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.

A284700 Number of edge covers in the n-antiprism graph.

Original entry on oeis.org

4, 13, 205, 2902, 41413, 590758, 8427370, 120219259, 1714968133, 24464596729, 348995693650, 4978540849669, 71020558255594, 1013132129923498, 14452670295681235, 206172198577335937, 2941115696724530533, 41956003773586931038, 598516493115066264085
Offset: 0

Views

Author

Eric W. Weisstein, Apr 01 2017

Keywords

Comments

Sequence extrapolated to n=0 using recurrence. - Andrew Howroyd, May 15 2017

Links

Crossrefs

Cf. A123304, A020866, A192742, A286910, A284699.

Programs

  • Mathematica
    Table[RootSum[4 - # - 18 #^2 - 13 #^3 + #^4 &, #^n &], {n, 0, 20}] (* Eric W. Weisstein, May 17 2017 *)
LinearRecurrence[{13, 18, 1, -4}, {13, 205, 2902, 41413}, {0, 20}] (* Eric W. Weisstein, May 17 2017 *)
CoefficientList[Series[(-x^3-36*x^2-39*x+4)/(4*x^4-x^3-18*x^2-13*x+1), {x, 0, 50}], x]
  • PARI
    Vec((-x^3-36*x^2-39*x+4)/(4*x^4-x^3-18*x^2-13*x+1)+O(x^20)) \\ Andrew Howroyd, May 15 2017

Formula

From Andrew Howroyd, May 15 2017 (Start)
a(n) = 13*a(n-1)+18*a(n-2)+a(n-3)-4*a(n-4) for n>=4.
G.f.: (-x^3-36*x^2-39*x+4)/(4*x^4-x^3-18*x^2-13*x+1).
(End)

Extensions

a(0)-a(2) and a(9)-a(18) from Andrew Howroyd, May 15 2017

A286911 Number of edge covers in the ladder graph P_2 x P_n.

Original entry on oeis.org

1, 7, 43, 277, 1777, 11407, 73219, 469981, 3016729, 19363879, 124293499, 797819173, 5121067777, 32871277183, 210995228083, 1354343064493, 8693301516841, 55800847838359, 358176305451691, 2299073773191541, 14757369859827601, 94725087867636847
Offset: 1

Views

Author

Andrew Howroyd, May 15 2017

Keywords

Links

Crossrefs

Row 2 of A286912.
Cf. A123304, A020866.

Programs

  • Mathematica
    Table[-RootSum[2 - 3 # - 6 #^2 + #^3 &, -14 #^n - 5 #^(n + 1) + #^(n + 2) &]/30, {n, 20}] (* Eric W. Weisstein, Aug 09 2017 *)
LinearRecurrence[{6, 3, -2}, {1, 7, 43}, 20] (* Eric W. Weisstein, Aug 09 2017 *)
CoefficientList[Series[(1 + x - 2 x^2)/(1 - 6 x - 3 x^2 + 2 x^3), {x, 0, 20}], x] (* Eric W. Weisstein, Aug 09 2017 *)

Formula

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

A284703 Number of maximal matchings in the n-prism graph.

Original entry on oeis.org

1, 5, 10, 17, 51, 98, 211, 457, 964, 2095, 4489, 9638, 20723, 44469, 95550, 205225, 440777, 946808, 2033571, 4367947, 9381928, 20151345, 43283195, 92967814, 199685501, 428904403, 921243124, 1978737477, 4250128177, 9128846128, 19607840133, 42115660425
Offset: 1

Views

Author

Eric W. Weisstein, Apr 01 2017

Keywords

Comments

Sequence extrapolated to n=1 using recurrence. - Andrew Howroyd, May 16 2017

Links

Crossrefs

Cf. A284701, A286945, A284710, A102080, A068397, A123304.

Programs

  • Magma
    I:=[1,5,10,17,51,98,211,457]; [n le 8 select I[n] else Self(n-1)+2*Self(n-2)+Self(n-3)-Self(n-4)+2*Self(n-5)+Self(n-6)-Self(n-7)-Self(n-8): n in [1..40]]; // Vincenzo Librandi, May 17 2017
  • Mathematica
    LinearRecurrence[{1, 2, 1, -1, 2, 1, -1, -1}, {1, 5, 10, 17, 51, 98, 211, 457}, 40] (* Vincenzo Librandi, May 17 2017 *)
CoefficientList[Series[(-8 x^7 - 7 x^6 + 6 x^5 + 10 x^4 - 4 x^3 + 3 x^2 + 4 x + 1) / ((x^2 - x + 1) (x^3 - x - 1) (x^3 + 2 x^2 + x - 1)), {x, 0, 33}], x] (* Vincenzo Librandi, May 17 2017 *)
Table[2 Cos[n Pi/3] + RootSum[-1 - 2 # - #^2 + #^3 &, #^n &] +
  RootSum[-1 + #^2 + #^3 &, #^n &], {n, 20}] (* Eric W. Weisstein, May 17 2017 *)
  • PARI
    Vec((-8*x^7-7*x^6+6*x^5+10*x^4-4*x^3+3*x^2+4*x+1)/((x^2-x+1)*(x^3-x-1)*(x^3+2*x^2+x-1))+O(x^20)) \\ Andrew Howroyd, May 16 2017

Formula

From Andrew Howroyd, May 16 2017 (Start)
a(n) = a(n-1)+2*a(n-2)+a(n-3)-a(n-4)+2*a(n-5)+a(n-6)-a(n-7)-a(n-8) for n>8.
G.f.: x*(-8*x^7-7*x^6+6*x^5+10*x^4 -4*x^3+3*x^2+4*x+1)/((x^2-x+1)*(x^3-x-1)*(x^3+2*x^2+x-1)).
(End)

Extensions

a(1)-a(2) and a(20)-a(32) from Andrew Howroyd, May 16 2017

A290700 Number of minimal edge covers in the n-prism graph.

Original entry on oeis.org

1, 5, 25, 49, 141, 389, 1009, 2761, 7441, 19925, 53769, 144721, 389325, 1048325, 2821665, 7594761, 20444065, 55029413, 148124153, 398713969, 1073231821, 2888859781, 7776063377, 20931130057, 56341150641, 151655712629, 408217654249, 1098815597201
Offset: 1

Views

Author

Eric W. Weisstein, Aug 09 2017

Keywords

Comments

The n-prism graph is well defined for n >= 3. Sequence extended to n = 1 using recurrence. - Andrew Howroyd, Aug 10 2017

Links

Crossrefs

Cf. A123304.

Programs

  • Mathematica
    Table[2 Cos[n Pi/2] + RootSum[-1 + # + #^2 + #^3 &, #^n &] -
  RootSum[1 - 2 #^2 - 2 #^3 + #^4 &, -2 #^(n + 2) - 2 #^(n + 3) + #^(n + 4) &], {n, 20}]
LinearRecurrence[{1, 2, 6, 2, 2, -2, -2, -1, 1}, {1, 5, 25, 49, 141, 389, 1009, 2761, 7441}, 20]
CoefficientList[Series[-( (1 + 4 x + 18 x^2 + 8 x^3 + 10 x^4 - 12 x^5 - 14 x^6 - 8 x^7 + 9 x^8)/((1 + x^2) (-1 - x - x^2 + x^3) (1 - 2 x - 2 x^2 + x^4))), {x, 0, 20}], x]
  • PARI
    Vec((1 + 4*x + 18*x^2 + 8*x^3 + 10*x^4 - 12*x^5 - 14*x^6 - 8*x^7 + 9*x^8)/((1 - 2*x - 2*x^2 + x^4)*(1 + x + x^2 - x^3)*(1 + x^2))+O(x^30)) \\ Andrew Howroyd, Aug 10 2017

Formula

From Andrew Howroyd, Aug 10 2017: (Start)
a(n) = a(n-1) + 2*a(n-2) + 6*a(n-3) + 2*a(n-4) + 2*a(n-5) - 2*a(n-6) - 2*a(n-7) - a(n-8) + a(n-9) for n > 9.
G.f.: x*(1 + 4*x + 18*x^2 + 8*x^3 + 10*x^4 - 12*x^5 - 14*x^6 - 8*x^7 + 9*x^8)/((1 - 2*x - 2*x^2 + x^4)*(1 + x + x^2 - x^3)*(1 + x^2)).
(End)

Extensions

a(1)-a(2) and terms a(9) and beyond from Andrew Howroyd, Aug 10 2017
Showing 1-4 of 4 results.

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