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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A094788 Number of (s(0), s(1), ..., s(2n+1)) such that 0 < s(i) < 10 and |s(i) - s(i-1)| = 1 for i = 1,2,...,2n+1, s(0) = 1, s(2n+1) = 6.

Original entry on oeis.org

1, 6, 27, 110, 428, 1624, 6069, 22458, 82555, 302082, 1101816, 4009616, 14567657, 52865230, 191684283, 694609494, 2515972324, 9110338728, 32981059485, 119377761602, 432046756571, 1563510554986, 5657752486512, 20472344560800
Offset: 2

Views

Author

Herbert Kociemba, Jun 15 2004

Keywords

Comments

Diagonal of the square array A217593. - Philippe Deléham, Mar 28 2013

Programs

  • Mathematica
    Drop[CoefficientList[Series[-x^2*(-1 + 2 x)/((x^2 - 3 x + 1) (5 x^2 - 5 x + 1)), {x, 0, 25}], x], 2] (* Michael De Vlieger, Aug 04 2021 *)
    LinearRecurrence[{8,-21,20,-5},{1,6,27,110},30] (* Harvey P. Dale, Aug 31 2021 *)
  • PARI
    Vec(x^2*(1-2*x)/(1-8*x+21*x^2-20*x^3+5*x^4)+O(x^66)) /* Joerg Arndt, Mar 29 2013 */

Formula

a(n) = (1/5)*Sum_{r=1..9} sin(r*Pi/10)*sin(3*r*Pi/5)*(2*cos(r*Pi/10))^(2*n+1).
a(n) = 8*a(n-1) - 21*a(n-2) + 20*a(n-3) - 5*a(n-4).
G.f.: -x^2*(-1+2*x) / ( (x^2-3*x+1)*(5*x^2-5*x+1) ).
a(n+2) = A217593(n,n+5). - Philippe Deléham, Mar 28 2013
2*a(n) = A030191(n-1) - A001906(n). - R. J. Mathar, Nov 15 2019

A342129 Square array T(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of g.f. 1/(1 - k*x + k*x^2).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 0, 0, 1, 3, 2, -1, 0, 1, 4, 6, 0, -1, 0, 1, 5, 12, 9, -4, 0, 0, 1, 6, 20, 32, 9, -8, 1, 0, 1, 7, 30, 75, 80, 0, -8, 1, 0, 1, 8, 42, 144, 275, 192, -27, 0, 0, 0, 1, 9, 56, 245, 684, 1000, 448, -81, 16, -1, 0, 1, 10, 72, 384, 1421, 3240, 3625, 1024, -162, 32, -1, 0
Offset: 0

Views

Author

Seiichi Manyama, Feb 28 2021

Keywords

Examples

			Square array begins:
  1,  1,  1, 1,   1,    1, ...
  0,  1,  2, 3,   4,    5, ...
  0,  0,  2, 6,  12,   20, ...
  0, -1,  0, 9,  32,   75, ...
  0, -1, -4, 9,  80,  275, ...
  0,  0, -8, 0, 192, 1000, ...
		

Crossrefs

Rows 0..1 give A000012, A001477.
Main diagonal gives (-1) * A109519(n+1).

Programs

  • Maple
    T:= (n, k)-> (<<0|1>, <-k|k>>^(n+1))[1, 2]:
    seq(seq(T(n, d-n), n=0..d), d=0..12); # Alois P. Heinz, Mar 01 2021
  • Mathematica
    T[n_, k_] := (-1)^n * Sum[If[k == j == 0, 1, (-k)^j] * Binomial[j, n - j], {j, 0, n}]; Table[T[k, n - k], {n, 0, 11}, {k, 0, n}] // Flatten (* Amiram Eldar, Apr 28 2021 *)
  • PARI
    T(n, k) = (-1)^n*sum(j=0, n\2, (-k)^(n-j)*binomial(n-j, j));
    
  • PARI
    T(n, k) = (-1)^n*sum(j=0, n, (-k)^j*binomial(j, n-j));
    
  • PARI
    T(n, k) = round(sqrt(k)^n*polchebyshev(n, 2, sqrt(k)/2));

Formula

T(0,k) = 1, T(1,k) = k and T(n,k) = k*(T(n-1,k) - T(n-2,k)) for n > 1.
T(n,k) = (-1)^n * Sum_{j=0..floor(n/2)} (-k)^(n-j) * binomial(n-j,j) = (-1)^n * Sum_{j=0..n} (-k)^j * binomial(j,n-j).
T(n,k) = sqrt(k)^n * S(n, sqrt(k)) with S(n, x) := U(n, x/2), Chebyshev's polynomials of the 2nd kind.

A112091 Number of idempotent order-preserving partial transformations (of an n-element chain).

Original entry on oeis.org

1, 2, 6, 21, 76, 276, 1001, 3626, 13126, 47501, 171876, 621876, 2250001, 8140626, 29453126, 106562501, 385546876, 1394921876, 5046875001, 18259765626, 66064453126, 239023437501, 864794921876, 3128857421876, 11320312500001
Offset: 0

Views

Author

Abdullahi Umar, Aug 25 2008

Keywords

Examples

			a(2) = 6 because there are exactly 6 idempotent order-preserving partial transformations (on a 2-element chain), namely: the empty map, (1)->(1), (2)->(2), (1,2)->(1,1), (1,2)->(1,2), (1,2)->(2,2); the mappings are coordinate-wise.
		

Programs

  • Magma
    [ n eq 1 select 1 else n eq 2 select 2 else n eq 3 select 6 else 6*Self(n-1)-10*Self(n-2)+ 5*Self(n-3): n in [1..30]]; // Vincenzo Librandi, Aug 21 2011
    
  • Mathematica
    RecurrenceTable[{a[0]==1,a[1]==2,a[n]==1+5(a[n-1]-a[n-2])},a[n], {n,30}] (* or *) LinearRecurrence[{6,-10,5},{1,2,6},31] (* Harvey P. Dale, Aug 20 2011 *)
  • PARI
    Vec((2*x-1)^2/(1-x)/(1-5*x+5*x^2)+O(x^99)) \\ Charles R Greathouse IV, Aug 21 2011

Formula

a(n) = ((sqrt(5))^(n - 1))*(((sqrt(5) + 1)/2)^n - ((sqrt(5) - 1)/2)^n) + 1. [corrected by Jason Yuen, Sep 06 2024]
a(n) = 1 + 5*(a(n-1) - a(n-2)), a(0) = 1, a(1) = 2.
G.f.: (1 - 2*x)^2/((1 - x)*(1 - 5*x + 5*x^2)). Convolution of A081567 with the sequence 1, -1, -1, -1 (-1 continued). - R. J. Mathar, Sep 06 2008
a(n) = 1 + A030191(n-1). - R. J. Mathar, Jun 20 2011
a(n) = 6*a(n-1) - 10*a(n-2) + 5*a(n-3); a(0) = 1, a(1) = 2, a(2) = 6. - Harvey P. Dale, Aug 20 2011
E.g.f.: exp(x) + (exp((5 + sqrt(5))*x/2) - exp((5 - sqrt(5))*x/2))/sqrt(5). - Franck Maminirina Ramaharo, Nov 09 2018

A217593 Square array T, read by antidiagonals: T(n,k) = 0 if n-k >=1 or if k-n >= 9, T(0,k) = 1 for k = 0..8, T(n,k) = T(n-1,k) + T(n,k-1).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 0, 0, 1, 3, 2, 0, 0, 1, 4, 5, 0, 0, 0, 1, 5, 9, 5, 0, 0, 0, 1, 6, 14, 14, 0, 0, 0, 0, 1, 7, 20, 28, 14, 0, 0, 0, 0, 0, 8, 27, 48, 42, 0, 0, 0, 0, 0, 0, 8, 35, 75, 90, 42, 0, 0, 0, 0, 0, 0, 0, 43, 110, 165, 132, 0, 0, 0, 0, 0, 0, 0, 0, 43, 153, 275, 297, 132, 0, 0, 0, 0, 0, 0, 0, 0, 0, 196, 428, 572, 429, 0, 0, 0, 0, 0, 0, 0
Offset: 0

Views

Author

Philippe Deléham, Mar 18 2013

Keywords

Examples

			Square array begins :
1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, ...
0, 1, 2, 3, 4, 5, 6, 7, 8, 8, 0, 0, ...
0, 0, 2, 5, 9, 14, 20, 27, 35, 43, 43, 0, 0, ...
0, 0, 0, 5, 14, 28, 75, 110, 153, 196, 196, 0, 0, ....
0, 0, 0, 0, 14, 42, 90, 165, 275, 428, 624, 820, 820, 0, 0, ...
...
Square array, read by rows, with 0 omitted:
1, 1, 1, 1, 1, 1, 1, 1, 1
1, 2, 3, 4, 5, 6, 7, 8, 8
2, 5, 9, 14, 20, 27, 35, 43, 43
5, 14, 28, 48, 75, 110, 153, 196, 196
14, 42, 90, 165, 275, 428, 624, 820, 820
42, 132, 297, 572, 1000, 1624, 2444, 3264, 3264
132, 429, 1001, 2001, 3625, 6069, 9333, 12597, 12597
429, 1430, 3431, 7056, 13125, 22458, 35055, 47652, 47652
...
		

References

  • A hexagon arithmetic of E. Lucas.

Formula

T(n,n) = A033191(n).
T(n,n+1) = A033191(n+1).
T(n,n+2) = A033190(n+1).
T(n,n+3) = A094667(n+1).
T(n,n+4) = A093131(n+1) = A030191(n).
T(n,n+5) = A094788(n+2).
T(n,n+6) = A094825(n+3).
T(n,n+7) = T(n,n+8) = A094865(n+3).
Sum_{k, 0<=k<=n} T(n-k,k) = A178381(n).

A081576 Square array of binomial transforms of Fibonacci numbers, read by antidiagonals.

Original entry on oeis.org

0, 0, 1, 0, 1, 1, 0, 1, 3, 2, 0, 1, 5, 8, 3, 0, 1, 7, 20, 21, 5, 0, 1, 9, 38, 75, 55, 8, 0, 1, 11, 62, 189, 275, 144, 13, 0, 1, 13, 92, 387, 905, 1000, 377, 21, 0, 1, 15, 128, 693, 2305, 4256, 3625, 987, 34, 0, 1, 17, 170, 1131, 4955, 13392, 19837, 13125, 2584, 55
Offset: 0

Views

Author

Paul Barry, Mar 22 2003

Keywords

Comments

Array rows are solutions of the recurrence a(n) = (2*k+1)*a(n-1) - A028387(k-1)*a(n-2) where a(0) = 0 and a(1) = 1.

Examples

			Square array begins as:
  0, 1,  1,   2,    3,    5,     8, ... A000045;
  0, 1,  3,   8,   21,   55,   144, ... A001906;
  0, 1,  5,  20,   75,  275,  1000, ... A030191;
  0, 1,  7,  38,  189,  905,  4256, ... A099453;
  0, 1,  9,  62,  387, 2305, 13392, ... A081574;
  0, 1, 11,  92,  693, 4955, 34408, ... A081575;
  0, 1, 13, 128, 1131, 9455, 76544, ...
The antidiagonal triangle begins as:
  0;
  0, 1;
  0, 1,  1;
  0, 1,  3,  2;
  0, 1,  5,  8,   3;
  0, 1,  7, 20,  21,   5;
  0, 1,  9, 38,  75,  55,   8;
  0, 1, 11, 62, 189, 275, 144, 13;
		

Crossrefs

Array row n: A000045 (n=0), A001906 (n=1), A030191 (n=2), A099453 (n=3), A081574 (n=4), A081575 (n=5).
Array columns k: A005408 (k=3), A077588 (k=4).

Programs

  • Magma
    A081576:= func< n,k | (&+[Binomial(k,j)*Fibonacci(j)*(n-k)^(k-j): j in [0..k]]) >;
    [A081576(n,k): k in [0..n], n in [0..12]]; // G. C. Greubel, May 26 2021
    
  • Mathematica
    T[n_, k_]:= If[n==0, Fibonacci[k], Sum[Binomial[k, j]*Fibonacci[j]*n^(k-j), {j, 0, k}]]; Table[T[n-k, k], {n,0,12}, {k,0,n}] //Flatten (* G. C. Greubel, May 26 2021 *)
  • Sage
    def A081576(n,k): return sum( binomial(k,j)*fibonacci(j)*(n-k)^(k-j) for j in (0..k) )
    flatten([[A081576(n,k) for k in (0..n)] for n in (0..12)]) # G. C. Greubel, May 26 2021

Formula

Rows are successive binomial transforms of F(n).
T(n, k) = ( ( (2*n + 1 + sqrt(5))/2 )^k - ( (2*n + 1 - sqrt(5))/2 )^k )/sqrt(5).
From G. C. Greubel, May 26 2021: (Start)
T(n, k) = Sum_{j=0..k} binomial(k,j)*Fibonacci(j)*n^(k-j) with T(0, k) = Fibonacci(k) (square array).
T(n, k) = Sum_{j=0..k} binomial(k,j)*Fibonacci(j)*(n-k)^(k-j) (antidiagonal triangle). (End)

A084330 a(0)=0, a(1)=1, a(n) = 31*a(n-1) - 29*a(n-2).

Original entry on oeis.org

0, 1, 31, 932, 27993, 840755, 25251608, 758417953, 22778659911, 684144336604, 20547893297305, 617144506454939, 18535590794481264, 556706123941725953, 16720357709153547887, 502186611389449931860, 15082894579507494998937, 453006320234438296943107
Offset: 0

Views

Author

Benoit Cloitre, Jun 21 2003

Keywords

Crossrefs

Cf. A030191.

Programs

  • Magma
    I:=[0,1]; [n le 2 select I[n] else 31*Self(n-1)-29*Self(n-2): n in [1..20]]; // Vincenzo Librandi, Jun 02 2015
  • Maple
    f:=proc(n) option remember; if n <=1 then n else 31*f(n-1)-29*f(n-2); fi; end;
  • Mathematica
    LinearRecurrence[{31,-29},{0,1},30] (* Harvey P. Dale, Jul 11 2014 *)
  • PARI
    a(n)=(1/13)*sum(k=0,n,binomial(n,k)*fibonacci(7*k))
    

Formula

a(n) = (1/13)*sum(k=0, n, binomial(n, k)*F(7*k)) where F(k) denotes the k-th Fibonacci number.
G.f.: x / (29*x^2-31*x+1). - Colin Barker, Jun 26 2013

Extensions

Corrected by N. J. A. Sloane, Sep 16 2005

A087453 a(n) = S(n,5), where S(n,m) = Sum_{k=0..n} binomial(n,k)*Fibonacci(m*k).

Original entry on oeis.org

0, 5, 65, 790, 9555, 115525, 1396720, 16886585, 204161685, 2468349470, 29842764575, 360804095305, 4362182828640, 52739531723965, 637629901296505, 7709053867890950, 93203771368320795, 1126849435241369885, 13623801173086279760, 164714071462466568145
Offset: 0

Views

Author

Benoit Cloitre, Oct 23 2003

Keywords

Crossrefs

Cf. A001906 (S(n,1)), A030191 (S(n,2)).

Programs

  • Magma
    I:=[0,5]; [n le 2 select I[n] else 13*Self(n-1)-11*Self(n-2): n in [1..20]]; // Vincenzo Librandi, Apr 27 2015
  • Mathematica
    Table[Sum[Binomial[n,k]Fibonacci[5k],{k,0,n}],{n,0,20}] (* Harvey P. Dale, Sep 03 2014 *)
    LinearRecurrence[{13, -11}, {0, 5}, 20] (* Vincenzo Librandi, Apr 27 2015 *)
  • PARI
    concat(0, Vec(5*x/(11*x^2-13*x+1) + O(x^100))) \\ Colin Barker, Apr 27 2015
    

Formula

a(n) = 13*a(n-1)-11*a(n-2).
a(n) = (1/sqrt(5))*(((13+5*sqrt(5))/2)^n-((13-5*sqrt(5))/2)^n).
G.f.: 5*x / (11*x^2-13*x+1). - Colin Barker, Apr 27 2015

A087635 a(n) = S(n,3) where S(n,m) = Sum_{k=0..n} binomial(n,k)*Fibonacci(m*k).

Original entry on oeis.org

0, 2, 12, 64, 336, 1760, 9216, 48256, 252672, 1323008, 6927360, 36272128, 189923328, 994451456, 5207015424, 27264286720, 142757658624, 747488804864, 3913902194688, 20493457948672, 107305138913280, 561857001684992
Offset: 0

Views

Author

Benoit Cloitre, Oct 23 2003

Keywords

Crossrefs

Cf. A000045, A001906 (S(n, 1)), A030191 (S(n, 2)).
Cf. A084326.

Programs

  • Mathematica
    LinearRecurrence[{6,-4}, {0, 2}, 22] (* Amiram Eldar, Apr 29 2025 *)

Formula

a(n) = 6*a(n-1)-4*a(n-2) = 2*A084326(n).
a(n) = Sum_{0<=j<=i<=n} C(i,j)*C(n,i)*Fibonacci(i+j). - Benoit Cloitre, May 21 2005
a(n) = 2^n*Fibonacci(2*n). - Benoit Cloitre, Sep 13 2005
a(n) = Sum_{k=0..n} C(n,k)*Fibonacci(k)*Lucas(n-k). - Ross La Haye, Aug 14 2006
G.f.: 2*x/(1-6*x+4*x^2). - Colin Barker, Jun 19 2012

A099449 An Alexander sequence for the knot 7_6.

Original entry on oeis.org

1, 5, 18, 60, 197, 650, 2153, 7140, 23682, 78545, 260498, 863945, 2865282, 9502740, 31515953, 104523050, 346651997, 1149675660, 3812913618, 12645575405, 41939208002, 139091904605, 461300030418, 1529907284460, 5073956524397
Offset: 0

Views

Author

Paul Barry, Oct 16 2004

Keywords

Comments

The denominator is a parameterization of the Alexander polynomial for the knot 7_6. The g.f. is the image of the g.f. of A030191 under the modified Chebyshev transform A(x)->(1/(1+x^2)^2)A(x/(1+x^2))

Crossrefs

Programs

  • Magma
    I:=[1,5,18,60,197,650,2153,7140]; [n le 8 select I[n] else 5*Self(n-1)-7*Self(n-2)+5*Self(n-3)-Self(n-4) : n in [1..30]]; // Vincenzo Librandi, Feb 12 2014
  • Mathematica
    CoefficientList[Series[(1 - x) (x + 1) (x^2 + 1)/(x^4 -5 x^3 + 7 x^2 - 5 x + 1), {x, 0, 40}], x] (* Vincenzo Librandi, Feb 12 2014 *)
    LinearRecurrence[{5,-7,5,-1},{1,5,18,60,197},30] (* Harvey P. Dale, Oct 06 2015 *)
  • PARI
    Vec(-(x-1)*(x+1)*(x^2+1)/(x^4-5*x^3+7*x^2-5*x+1) + O(x^100)) \\ Colin Barker, Feb 10 2014
    

Formula

G.f.: -(x-1)*(x+1)*(x^2+1) / (x^4-5*x^3+7*x^2-5*x+1). - Colin Barker, Feb 10 2014
a(n) = A099448(n) - A099448(n-2).
a(n) = 5*a(n-1)-7*a(n-2)+5*a(n-3)-a(n-4) for n>4. - Colin Barker, Feb 10 2014

Extensions

G.f. corrected by Colin Barker, Feb 10 2014

A167925 Triangle, T(n, k) = (sqrt(k+1))^(n-1)*ChebyshevU(n-1, sqrt(k+1)/2), read by rows.

Original entry on oeis.org

0, 1, 1, 1, 2, 3, 0, 2, 6, 12, -1, 0, 9, 32, 75, -1, -4, 9, 80, 275, 684, 0, -8, 0, 192, 1000, 3240, 8232, 1, -8, -27, 448, 3625, 15336, 47677, 122368, 1, 0, -81, 1024, 13125, 72576, 276115, 835584, 2158569, 0, 16, -162, 2304, 47500, 343440, 1599066, 5705728, 16953624, 44010000
Offset: 0

Views

Author

Roger L. Bagula, Nov 15 2009

Keywords

Examples

			Triangle begins as:
   0;
   1,  1;
   1,  2,   3;
   0,  2,   6,   12;
  -1,  0,   9,   32,    75;
  -1, -4,   9,   80,   275,   684;
   0, -8,   0,  192,  1000,  3240,   8232;
   1, -8, -27,  448,  3625, 15336,  47677, 122368;
   1,  0, -81, 1024, 13125, 72576, 276115, 835584, 2158569;
		

Crossrefs

Programs

  • Magma
    A167925:= func< n,k | Round((Sqrt(k+1))^(n-1)*Evaluate(ChebyshevSecond(n), Sqrt(k+1)/2)) >;
    [A167925(n,k): k in [0..n], n in [0..12]]; // G. C. Greubel, Sep 11 2023
    
  • Mathematica
    (* First program *)
    m[k_]= {{k,1}, {-1,1}};
    v[0, k_]:= {0,1};
    v[n_, k_]:= v[n, k]= m[k].v[n-1,k];
    T[n_, k_]:= v[n, k][[1]];
    Table[T[n, k], {n,0,12}, {k,0,n}]//Flatten
    (* Second program *)
    A167925[n_, k_]:= (Sqrt[k+1])^(n-1)*ChebyshevU[n-1, Sqrt[k+1]/2];
    Table[A167925[n, k], {n,0,12}, {k,0,n}]//Flatten (* G. C. Greubel, Sep 11 2023 *)
  • SageMath
    def A167925(n,k): return (sqrt(k+1))^(n-1)*chebyshev_U(n-1, sqrt(k+1)/2)
    flatten([[A167925(n,k) for k in range(n+1)] for n in range(13)]) # G. C. Greubel, Sep 11 2023

Formula

T(n, k) = (-1)^(n+1) * [x^(n-1)]( 1/(1 + (k+1)*x + (k+1)*x^2) ). - Francesco Daddi, Aug 04 2011 (modified by G. C. Greubel, Sep 11 2023)
From G. C. Greubel, Sep 11 2023: (Start)
T(n, k) = (sqrt(k+1))^(n-1)*ChebyshevU(n-1, sqrt(k+1)/2).
T(n, 0) = A128834(n).
T(n, 1) = A009545(n) = A099087(n-1).
T(n, 2) = A057083(n-1).
T(n, 3) = A001787(n).
T(n, 4) = A030191(n-1).
T(n, 5) = A030192(n-1).
T(n, 6) = A030240(n-1).
T(n, 7) = A057084(n-1).
T(n, 8) = A057085(n).
T(n, 9) = A057086(n-1).
T(n, 10) = A190871(n).
T(n, 11) = A190873(n). (End)

Extensions

Edited by G. C. Greubel, Sep 11 2023
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