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.

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A180250 a(n) = 5*a(n-1) + 10*a(n-2), with a(1)=0 and a(2)=1.

Original entry on oeis.org

0, 1, 5, 35, 225, 1475, 9625, 62875, 410625, 2681875, 17515625, 114396875, 747140625, 4879671875, 31869765625, 208145546875, 1359425390625, 8878582421875, 57987166015625, 378721654296875, 2473479931640625, 16154616201171875, 105507880322265625
Offset: 1

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Author

Keywords

Crossrefs

Programs

  • Magma
    [n le 2 select n-1 else 5*Self(n-1) +10*Self(n-2): n in [1..30]]; // G. C. Greubel, Jan 16 2018
    
  • Mathematica
    Join[{a=0,b=1},Table[c=5*b+10*a;a=b;b=c,{n,100}]]
    LinearRecurrence[{5,10}, {0,1}, 30] (* G. C. Greubel, Jan 16 2018 *)
  • PARI
    a(n)=([0,1;10,5]^(n-1))[1,2] \\ Charles R Greathouse IV, Oct 03 2016
    
  • PARI
    my(x='x+O('x^30)); concat([0], Vec(x^2/(1-5*x-10*x^2))) \\ G. C. Greubel, Jan 16 2018
    
  • SageMath
    A180250= BinaryRecurrenceSequence(5,10,0,1)
    [A180250(n-1) for n in range(1,41)] # G. C. Greubel, Jul 21 2023

Formula

a(n) = ((5+sqrt(65))^(n-1) - (5-sqrt(65))^(n-1))/(2^(n-1)*sqrt(65)). - Rolf Pleisch, May 14 2011
G.f.: x^2/(1-5*x-10*x^2).
a(n) = (i*sqrt(10))^(n-1) * ChebyshevU(n-1, -i*sqrt(5/8)). - G. C. Greubel, Jul 21 2023

A015551 Expansion of x/(1 - 6*x - 5*x^2).

Original entry on oeis.org

0, 1, 6, 41, 276, 1861, 12546, 84581, 570216, 3844201, 25916286, 174718721, 1177893756, 7940956141, 53535205626, 360916014461, 2433172114896, 16403612761681, 110587537144566, 745543286675801, 5026197405777636
Offset: 0

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Author

Keywords

Comments

Let the generator matrix for the ternary Golay G_12 code be [I|B], where the elements of B are taken from the set {0,1,2}. Then a(n)=(B^n)1,2 for instance. - _Paul Barry, Feb 13 2004
Pisano period lengths: 1, 2, 4, 4, 1, 4, 42, 8, 12, 2, 10, 4, 12, 42, 4, 16, 96, 12, 360, 4, ... - R. J. Mathar, Aug 10 2012

Crossrefs

Programs

  • Magma
    I:=[0,1]; [n le 2 select I[n] else 6*Self(n-1)+5*Self(n-2): n in [1..30]]; // Vincenzo Librandi, Nov 14 2011
    
  • Mathematica
    Join[{a=0,b=1},Table[c=6*b+5*a;a=b;b=c,{n,100}]] (* Vladimir Joseph Stephan Orlovsky, Jan 16 2011 *)
    CoefficientList[Series[x/(1-6x-5x^2),{x,0,20}],x] (* or *) LinearRecurrence[ {6,5},{0,1},30] (* Harvey P. Dale, Oct 30 2017 *)
  • PARI
    a(n)=([0,1; 5,6]^n*[0;1])[1,1] \\ Charles R Greathouse IV, Oct 03 2016
  • Sage
    [lucas_number1(n,6,-5) for n in range(0, 21)] # Zerinvary Lajos, Apr 24 2009
    

Formula

a(n) = 6*a(n-1) + 5*a(n-2).
a(n) = sqrt(14)*(3+sqrt(14))^n/28 - sqrt(14)*(3-sqrt(14))^n/28. - Paul Barry, Feb 13 2004

A086901 a(1) = a(2) = 1; for n>2, a(n) = 4*a(n-1) + 3*a(n-2).

Original entry on oeis.org

1, 1, 7, 31, 145, 673, 3127, 14527, 67489, 313537, 1456615, 6767071, 31438129, 146053729, 678529303, 3152278399, 14644701505, 68035641217, 316076669383, 1468413601183, 6821884412881, 31692778455073, 147236767058935
Offset: 1

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Author

Rick Powers (rick.powers(AT)mnsu.edu), Sep 18 2003

Keywords

Examples

			a(3) = 4*1 + 3*1 = 7;
a(4) = 4*7 + 3*1 = 31.
		

Crossrefs

Programs

  • Haskell
    a086901 n = a086901_list !! (n-1)
    a086901_list = 1 : 1 : zipWith (+)
                   (map (* 3) a086901_list) (map (* 4) $ tail a086901_list)
    -- Reinhard Zumkeller, Feb 13 2015
    
  • Magma
    [n le 2 select 1 else 4*Self(n-1) +3*Self(n-2): n in [1..41]]; // G. C. Greubel, Oct 28 2024
    
  • Mathematica
    a[n_]:=(MatrixPower[{{3,2},{3,1}},n].{{2},{1}})[[2,1]]; Table[a[n],{n,0,40}] (* Vladimir Joseph Stephan Orlovsky, Feb 20 2010 *)
    Transpose[NestList[Flatten[{Rest[#],ListCorrelate[{3,4},#]}]&, {1,1},40]][[1]]  (* Harvey P. Dale, Mar 23 2011 *)
    LinearRecurrence[{4,3}, {1,1}, 41] (* G. C. Greubel, Oct 28 2024 *)
  • PARI
    A086901(n)=if(n<3,1,4*A086901(n-1)+3*A086901(n-2)) \\ Michael B. Porter, Apr 04 2010
    
  • SageMath
    A086901=BinaryRecurrenceSequence(4,3,1,1)
    [A086901(n) for n in range(41)] # G. C. Greubel, Oct 28 2024

Formula

a(n) = ((c + 5)*b^n - (b + 5)*c^n)/14, where b = 2 + sqrt(7), c = 2 - sqrt(7).
From Ralf Stephan, Feb 01 2004: (Start)
G.f.: x*(1-3*x)/(1 - 4*x - 3*x^2).
a(n) = A015530(n) - 3*A015530(n-1) = 1 + 6*Sum_{k=0..n-2} A015530(k). (End)
a(n+1) = Sum_{k=0..n} 3^(n-k)*A122542(n,k), n>=0. - Philippe Deléham, Oct 27 2006
a(n) = upper left term in the 2 X 2 matrix [1,2; 3,3]^(n-1). - Gary W. Adamson, Mar 02 2008
G.f.: G(0)*(1-3*x)/(2-4*x), where G(k) = 1 + 1/(1 - x*(7*k-4)/(x*(7*k+3) - 2/G(k+1))); (continued fraction). - Sergei N. Gladkovskii, Jun 16 2013
E.g.f.: exp(2*x)*( cosh(sqrt(7)*x) - (1/sqrt(7))*sinh(sqrt(7)*x) ). - G. C. Greubel, Oct 28 2024

Extensions

More terms from Ray Chandler, Sep 19 2003

A080042 a(n) = 4*a(n-1)+3*a(n-2) for n>1, a(0)=2, a(1)=4.

Original entry on oeis.org

2, 4, 22, 100, 466, 2164, 10054, 46708, 216994, 1008100, 4683382, 21757828, 101081458, 469599316, 2181641638, 10135364500, 47086382914, 218751625156, 1016265649366, 4721317472932, 21934066839826, 101900219778100
Offset: 0

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Author

Mario Catalani (mario.catalani(AT)unito.it), Jan 21 2003

Keywords

Comments

This is the Lucas sequence V(4,-3). [Bruno Berselli, Jan 09 2013]

Crossrefs

Cf. A015530: Lucas sequence U(4,-3).

Programs

  • Mathematica
    CoefficientList[Series[(2 - 4 t)/(1 - 4 t - 3 t^2), {t, 0, 25}], t]
  • Sage
    [lucas_number2(n,4,-3) for n in range(0, 22)] # Zerinvary Lajos, May 14 2009

Formula

G.f.: (2-4*x)/(1-4*x-3*x^2).
a(n) = (2+sqrt(7))^n+(2-sqrt(7))^n.
G.f.: G(0)/x -2/x, where G(k)= 1 + 1/(1 - x*(7*k-4)/(x*(7*k+3) - 2/G(k+1))); (continued fraction). - Sergei N. Gladkovskii, Jun 03 2013
a(n) = [x^n] ( (1 + 4*x + sqrt(1 + 8*x + 28*x^2))/2 )^n for n >= 1. - Peter Bala, Jun 23 2015

A189800 a(n) = 6*a(n-1) + 8*a(n-2), with a(0)=0, a(1)=1.

Original entry on oeis.org

0, 1, 6, 44, 312, 2224, 15840, 112832, 803712, 5724928, 40779264, 290475008, 2069084160, 14738305024, 104982503424, 747801460736, 5326668791808, 37942424436736, 270267896954880, 1925146777223168, 13713023838978048, 97679317251653632, 695780094221746176
Offset: 0

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Author

Keywords

Crossrefs

Programs

  • Magma
    I:=[0,1]; [n le 2 select I[n] else 6*Self(n-1)+8*Self(n-2): n in [1..30]]; // Vincenzo Librandi, Nov 14 2011
    
  • Mathematica
    LinearRecurrence[{6, 8}, {0, 1}, 50]
    CoefficientList[Series[-(x/(-1+6 x+8 x^2)),{x,0,50}],x] (* Harvey P. Dale, Jul 26 2011 *)
  • PARI
    a(n)=([0,1; 8,6]^n*[0;1])[1,1] \\ Charles R Greathouse IV, Oct 03 2016

Formula

G.f.: x/(1 - 2*x*(3+4*x)). - Harvey P. Dale, Jul 26 2011

A015541 Expansion of x/(1 - 5*x - 7*x^2).

Original entry on oeis.org

0, 1, 5, 32, 195, 1199, 7360, 45193, 277485, 1703776, 10461275, 64232807, 394392960, 2421594449, 14868722965, 91294775968, 560554940595, 3441838134751, 21133075257920, 129758243232857, 796722742969725, 4891921417478624, 30036666288181195
Offset: 0

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Author

Keywords

Comments

Pisano period lengths: 1, 3, 8, 6, 8, 24, 6, 6, 24, 24, 5, 24, 12, 6, 8, 12, 16, 24, 120, 24, ... - R. J. Mathar, Aug 10 2012

Crossrefs

Programs

Formula

a(n) = 5*a(n-1) + 7*a(n-2).

A015544 Lucas sequence U(5,-8): a(n+1) = 5*a(n) + 8*a(n-1), a(0)=0, a(1)=1.

Original entry on oeis.org

0, 1, 5, 33, 205, 1289, 8085, 50737, 318365, 1997721, 12535525, 78659393, 493581165, 3097180969, 19434554165, 121950218577, 765227526205, 4801739379641, 30130517107845, 189066500576353, 1186376639744525, 7444415203333449, 46713089134623445
Offset: 0

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Author

Keywords

Crossrefs

Programs

  • Magma
    [n le 2 select n-1 else 5*Self(n-1) + 8*Self(n-2): n in [1..30]]; // Vincenzo Librandi, Nov 13 2012
    
  • Mathematica
    a[n_]:=(MatrixPower[{{1,2},{1,-6}},n].{{1},{1}})[[2,1]]; Table[Abs[a[n]],{n,-1,40}] (* Vladimir Joseph Stephan Orlovsky, Feb 19 2010 *)
    LinearRecurrence[{5, 8}, {0, 1}, 30] (* Vincenzo Librandi, Nov 13 2012 *)
  • PARI
    A015544(n)=imag((2+quadgen(57))^n) \\ M. F. Hasler, Mar 06 2009
    
  • PARI
    x='x+O('x^30); concat([0], Vec(x/(1 - 5*x - 8*x^2))) \\ G. C. Greubel, Jan 01 2018
  • Sage
    [lucas_number1(n,5,-8) for n in range(0, 21)] # Zerinvary Lajos, Apr 24 2009
    

Formula

a(n) = 5*a(n-1) + 8*a(n-2).
G.f.: x/(1 - 5*x - 8*x^2). - M. F. Hasler, Mar 06 2009

Extensions

More precise definition by M. F. Hasler, Mar 06 2009

A102756 Triangle T(n,k), 0<=k<=n, read by rows defined by: T(n,k) = T(n-1,k-1) + 2*T(n-1,k) + T(n-2,k-2) - T(n-2,k), T(0,0) = 1, T(n,k) = 0 if k < 0 or if n < k.

Original entry on oeis.org

1, 2, 1, 3, 4, 2, 4, 10, 10, 3, 5, 20, 31, 20, 5, 6, 35, 76, 78, 40, 8, 7, 56, 161, 232, 184, 76, 13, 8, 84, 308, 582, 636, 406, 142, 21, 9, 120, 546, 1296, 1831, 1604, 861, 260, 34, 10, 165, 912, 2640, 4630, 5215, 3820, 1766, 470, 55
Offset: 0

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Author

Philippe Deléham, Dec 18 2006

Keywords

Comments

Rising and falling diagonals are A008999, A124400.
Subtriangle of triangle given by (1, 1, -1, 1, 0, 0, 0, 0, 0, 0, 0, ...) DELTA (0, 1, 1, -1, 0, 0, 0, 0, 0, 0, 0, ...) where DELTA is the operator defined in A084938. - Philippe Deléham, Feb 17 2012
Jointly generated with A209130 as an array of coefficients of polynomials u(n,x): initially, u(1,x)=v(1,x)=1; for n>1, u(n,x)=u(n-1,x)+(x+1)*v(n-1)x and v(n,x)=x*u(n-1,x)+(x+1)*v(n-1,x). See the Mathematica section. - Clark Kimberling, Mar 05 2012

Examples

			Triangle begins:
  1;
  2, 1;
  3, 4, 2;
  4, 10, 10, 3;
  5, 20, 31, 20, 5;
  6, 35, 76, 78, 40, 8;
  7, 56, 161, 232, 184, 76, 13;
  8, 84, 308, 582, 636, 406, 142, 21;
  9, 120, 546, 1296, 1831, 1604, 861, 260, 34;
  10, 165, 912, 2640, 4630, 5215, 3820, 1766, 470, 55;
Triangle (1, 1, -1, 1, 0, 0, ...) DELTA (0, 1, 1, -1, 0, 0, ...) begins:
  1
  1, 0
  2, 1, 0
  3, 4, 2, 0
  4, 10, 10, 3, 0
  5, 20, 31, 20, 5, 0
  6, 35, 76, 78, 40, 8, 0
  7, 56, 161, 232, 184, 76, 13, 0
		

Crossrefs

Programs

  • Mathematica
    u[1, x_] := 1; v[1, x_] := 1; z = 16;
    u[n_, x_] := u[n - 1, x] + (x + 1)*v[n - 1, x];
    v[n_, x_] := x*u[n - 1, x] + (x + 1)*v[n - 1, x];
    Table[Expand[u[n, x]], {n, 1, z/2}]
    Table[Expand[v[n, x]], {n, 1, z/2}]
    cu = Table[CoefficientList[u[n, x], x], {n, 1, z}];
    TableForm[cu]
    Flatten[%]    (* A102756 *)
    Table[Expand[v[n, x]], {n, 1, z}]
    cv = Table[CoefficientList[v[n, x], x], {n, 1, z}];
    TableForm[cv]
    Flatten[%]    (* A209130 *)
    (* Clark Kimberling, Mar 05 2012 *)

Formula

Sum_{k=0..n} x^k*T(n,k) = A254006(n), A000012(n), A000027(n+1), A000244(n), A015530(n+1), A015544(n+1) for x = -2, -1, 0, 1, 2, 3 respectively.
T(n,n-1) = 2*A001629(n+1) for n>=1.
T(n,n) = Fibonacci(n+1) = A000045(n+1).
T(n,0) = n+1.
T(n,1) = A000292(n) for n>=1.
T(n+1,2) = binomial(n+4,n-1)+binomial(n+2,n-1)= A051747(n) for n>=1.
G.f.: 1/(1-(2+y)*x+(1+y)*(1-y)*x^2). - Philippe Deléham, Feb 17 2012

A109115 a(n) = 4*a(n-1) + 3*a(n-2), a(0)=1, a(1)=6.

Original entry on oeis.org

1, 6, 27, 126, 585, 2718, 12627, 58662, 272529, 1266102, 5881995, 27326286, 126951129, 589783374, 2739986883, 12729297654, 59137151265, 274736498022, 1276357445883, 5929639277598, 27547629448041, 127979435624958
Offset: 0

Views

Author

Emeric Deutsch, Jun 19 2005

Keywords

Comments

Kekulé numbers for certain benzenoids.

References

  • S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 302, P_{12}).

Programs

  • Maple
    a[0]:=1: a[1]:=6: for n from 2 to 26 do a[n]:=4*a[n-1]+3*a[n-2] od: seq(a[n],n=0..26);
  • Mathematica
    LinearRecurrence[{4,3},{1,6},40] (* Harvey P. Dale, Aug 20 2020 *)

Formula

a(n) = ((sqrt(7) + 4)*(2 + sqrt(7))^n + (sqrt(7) - 4)*(2 - sqrt(7))^n)/(2*sqrt(7)).
G.f.: (1+2z)/(1 - 4z - 3z^2).
a(n) = A015530(n+1)+2*A015530(n). - R. J. Mathar, Jul 26 2022

A218986 Power floor sequence of 2+sqrt(7).

Original entry on oeis.org

4, 18, 83, 385, 1788, 8306, 38587, 179265, 832820, 3869074, 17974755, 83506241, 387949228, 1802315634, 8373110219, 38899387777, 180716881764, 839565690386, 3900413406835, 18120350698497, 84182643014492, 391091624153458, 1816914425657307, 8440932575089601
Offset: 0

Views

Author

Clark Kimberling, Nov 11 2012

Keywords

Comments

See A214992 for a discussion of power floor sequence and the power floor function, p1(x) = limit of a(n,x)/x^n. The present sequence is a(n,r), where r = 2+sqrt(7), and the limit p1(r) = 3.83798607113023840500712572585708...
See A218987 for the power floor function, p4. For comparison with p1, limit(p4(r)/p1(r) = 4-sqrt(7).

Examples

			a(0) = [r] = 4, where r = 2+sqrt(7);
a(1) = [4*r] = 18; a(2) = [18*r] = 83.
		

Crossrefs

Programs

  • Mathematica
    x = 2 + Sqrt[7]; z = 30; (* z = # terms in sequences *)
    f[x_] := Floor[x]; c[x_] := Ceiling[x];
    p1[0] = f[x]; p2[0] = f[x]; p3[0] = c[x]; p4[0] = c[x];
    p1[n_] := f[x*p1[n - 1]]
    p2[n_] := If[Mod[n, 2] == 1, c[x*p2[n - 1]], f[x*p2[n - 1]]]
    p3[n_] := If[Mod[n, 2] == 1, f[x*p3[n - 1]], c[x*p3[n - 1]]]
    p4[n_] := c[x*p4[n - 1]]
    t1 = Table[p1[n], {n, 0, z}]  (* A218986 *)
    t2 = Table[p2[n], {n, 0, z}]  (* A015530 *)
    t3 = Table[p3[n], {n, 0, z}]  (* A126473 *)
    t4 = Table[p4[n], {n, 0, z}]  (* A218987 *)
    LinearRecurrence[{5,-1,-3},{4,18,83},30] (* Harvey P. Dale, Jun 18 2014 *)
  • PARI
    a(n) = round((14+(161-61*sqrt(7))*(2-sqrt(7))^n+(2+sqrt(7))^n*(161+61*sqrt(7)))/84) \\ Colin Barker, Sep 02 2016
    
  • PARI
    Vec((4-2*x-3*x^2)/((1-x)*(1-4*x-3*x^2)) + O(x^30)) \\ Colin Barker, Sep 02 2016

Formula

a(n) = [x*a(n-1)], where x=2+sqrt(7), a(0) = [x].
a(n) = 5*a(n-1) - a(n-2) - 3*a(n-3).
G.f.: (4 - 2*x - 3*x^2)/(1 - 5*x + x^2 + 3*x^3).
a(n) = (14+(161-61*sqrt(7))*(2-sqrt(7))^n+(2+sqrt(7))^n*(161+61*sqrt(7)))/84. - Colin Barker, Sep 02 2016
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