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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A382848 a(n) = Sum_{k=0..n} (-1)^(n-k) * binomial(n,k)^2 * binomial(n+k,k).

Original entry on oeis.org

1, 1, -5, -35, -29, 751, 3991, -4115, -137885, -495269, 2114245, 25786795, 50109775, -627370925, -4643568305, -495798035, 157753390435, 768269873875, -1851203127335, -35924154988865, -107001450483779, 763444753890721, 7510024190977105, 8899910747771995
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 06 2025

Keywords

Comments

Diagonal of the rational function 1 / (1 + x + x*y + y*z + x*z + x*y*z).

Crossrefs

Programs

  • Mathematica
    Table[Sum[(-1)^(n - k) Binomial[n, k]^2 Binomial[n + k, k], {k, 0, n}], {n, 0, 23}]
    Table[(-1)^n HypergeometricPFQ[{-n, -n, n + 1}, {1, 1}, -1], {n, 0, 23}]
    Table[SeriesCoefficient[1/(1 + x + x y + y z + x z + x y z), {x, 0, n}, {y, 0, n}, {z, 0, n}], {n, 0, 23}]

Formula

(59*n-94)*n^2*a(n) = 5*(59*n^3-153*n^2+117*n-30)*a(n-1) - (2301*n^3-8268*n^2+9257*n-3050)*a(n-2) - 2*(59*n-35)*(n-2)^2*a(n-3) with a(0) = 1, a(1) = 1 and a(2) = -5. - Peter Bala, May 24 2025

A188289 Binomial sum related to rooted trees.

Original entry on oeis.org

0, 2, 3, 14, 45, 167, 609, 2270, 8517, 32207, 122463, 467843, 1794195, 6903353, 26635773, 103020254, 399300165, 1550554583, 6031074183, 23493410759, 91638191235, 357874310213, 1399137067683, 5475504511859, 21447950506395, 84083979575117
Offset: 0

Views

Author

Olivier Gérard, Aug 19 2012

Keywords

Crossrefs

Programs

  • GAP
    List([0..30], n-> Binomial(2*n,n) -(-1)^n -Sum([0..n-1], k-> Binomial(2*k,n-1))); # G. C. Greubel, Apr 29 2019
  • Magma
    [n eq 0 select 0 else Binomial(2*n, n) -(-1)^n - (&+[Binomial(2*k, n-1): k in [0..n-1]]): n in [0..30]]; // G. C. Greubel, Apr 29 2019
    
  • Mathematica
    Table[Binomial[2n,n]-(-1)^n-Sum[Binomial[2k,n-1],{k,0,n-1}],{n,0,30}] (* Harvey P. Dale, Dec 10 2012 *)
  • PARI
    {a(n) = binomial(2*n,n) -(-1)^n -sum(k=0,n-1, binomial(2*k,n-1))}; \\ G. C. Greubel, Apr 29 2019
    
  • Sage
    [binomial(2*n,n) -(-1)^n -sum(binomial(2*k, n-1) for k in (0..n-1)) for n in (0..30)] # G. C. Greubel, Apr 29 2019
    

Formula

a(n) = binomial(2*n,n) - (-1)^n - Sum_{k=0..n-1} binomial(2*k, n-1).
a(n) = Sum_{k=1..n} binomial(n+k,k)*(Sum_{r=n-k..n} (-1)^r*binomial(n-k, r)).
a(n) = (-1)^n*2^(-(1+n))*(1 - 2^(1+n) + (-2)^n*binomial(2+2*n, 1+n) * hypergeometric2F1(1, 2+2*n; 2+n; -1)).
a(n) = Sum_{k=1..n} (-1)^(n+k)*binomial(n+k,k). - Ridouane Oudra, Sep 07 2025

A191649 Number of lattice paths from (0,0) to (n,n) using steps (0,1), (1,0), (1,1), (2,2).

Original entry on oeis.org

1, 3, 14, 71, 379, 2082, 11651, 66051, 378064, 2180037, 12644861, 73695358, 431209313, 2531556197, 14904832196, 87970766447, 520337606401, 3083584244460, 18304476242735, 108820740004749, 647817646760368, 3861215365595659, 23039691494489015, 137615812845579390
Offset: 0

Views

Author

Joerg Arndt, Jun 30 2011

Keywords

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 30); Coefficients(R!( 1/Sqrt(x^4+2*x^3-x^2-6*x+1) )); // G. C. Greubel, Apr 29 2019
    
  • Mathematica
    CoefficientList[Series[1/Sqrt[x^4 + 2 x^3 - x^2 - 6 x + 1], {x, 0, 23}], x] (* Michael De Vlieger, Oct 08 2016 *)
  • PARI
    /* same as in A092566 but use */
    steps=[[0,1], [1,0], [1,1], [2,2]];
    /* Joerg Arndt, Jun 30 2011 */
    
  • PARI
    my(x='x+O('x^30)); Vec(1/sqrt(x^4+2*x^3-x^2-6*x+1)) \\ G. C. Greubel, Apr 29 2019
    
  • Sage
    (1/sqrt(x^4+2*x^3-x^2-6*x+1)).series(x, 30).coefficients(x, sparse=False) # G. C. Greubel, Apr 29 2019

Formula

G.f.: 1/sqrt(x^4 +2*x^3 -x^2 -6*x +1). - Mark van Hoeij, Apr 17 2013
D-finite with recurrence: n*a(n) +3*(-2*n+1)*a(n-1) +(-n+1)*a(n-2) +(2*n-3)*a(n-3) +(n-2)*a(n-4)=0. - R. J. Mathar, Oct 08 2016

A192371 Number of lattice paths from (0,0) to (n,n) using steps (1,1), (0,2), (2,0), (0,3), (3,0).

Original entry on oeis.org

1, 1, 3, 9, 25, 87, 307, 1113, 4149, 15605, 59201, 225999, 866449, 3333847, 12865335, 49769689, 192945411, 749396493, 2915432049, 11358771965, 44313108627, 173081422997, 676766482917, 2648843996031, 10376891445525, 40685535827325, 159641884780749, 626849029013919, 2463010645910537, 9683604464279235
Offset: 0

Views

Author

Joerg Arndt, Jul 01 2011

Keywords

Crossrefs

Programs

  • Maple
    s := RootOf( (s^3-s-1)*(s-1)+x*s*(4-3*s), s);
    ogf := sqrt(4*s-3*s^2)*(s^3-4*s^2+2*s+2)/((2*s^2-s-2)*(3*s^3-6*s^2+4*s-2)*(1-x)):
    series(ogf, x=0, 30);  # Mark van Hoeij, Apr 17 2013
    # second Maple program:
    b:= proc(p) b(p):= `if`(p=[0$2], 1, `if`(min(p[])<0, 0,
          add(b(p-l), l=[[1, 1], [0, 2], [2, 0], [0, 3], [3, 0]])))
        end:
    a:= n-> b([n$2]):
    seq(a(n), n=0..30);  # Alois P. Heinz, Aug 18 2014
  • Mathematica
    b[p_List] := b[p] = If[p == {0, 0}, 1, If[Min[p] < 0, 0, Sum[b[p - l], {l, {{1, 1}, {0, 2}, {2, 0}, {3, 0}, {0, 3}}}]]]; a[n_] := b[{n, n}]; Table[a[n], {n, 0, 30}] (* Jean-François Alcover, May 27 2015, after Alois P. Heinz *)
  • PARI
    /* same as in A092566 but use */
    steps=[[1,1], [2,0], [0,2], [3,0], [0,3]];
    /* Joerg Arndt, Jun 30 2011 */

Formula

G.f.: sqrt(4*s-3*s^2)*(s^3-4*s^2+2*s+2)/((2*s^2-s-2)*(3*s^3-6*s^2+4*s-2)*(1-x)) where the function s satisfies (s^3-s-1)*(s-1)+x*s*(4-3*s) = 0. - Mark van Hoeij, Apr 17 2013

A192417 Number of lattice paths from (0,0) to (n,n) using steps (0,1), (1,0), (2,2), (3,3).

Original entry on oeis.org

1, 2, 7, 27, 107, 436, 1810, 7609, 32288, 138009, 593311, 2562725, 11112720, 48347332, 210936119, 922550622, 4043488129, 17755735241, 78099099877, 344033901804, 1517535718392, 6701979806379, 29630948706756, 131136723532257, 580901892464599, 2575423975663301
Offset: 0

Views

Author

Joerg Arndt, Jun 30 2011

Keywords

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 30); Coefficients(R!( 1/Sqrt(x^6+2*x^5+x^4-2*x^3-2*x^2-4*x+1) )); // G. C. Greubel, Apr 29 2019
    
  • Mathematica
    CoefficientList[Series[1/Sqrt[x^6+2x^5+x^4-2x^3-2x^2-4x+1], {x, 0, 25}], x] (* Michael De Vlieger, Oct 08 2016 *)
  • PARI
    /* same as in A092566 but use */
    steps=[[0,1], [1,0], [2,2], [3,3]];
    /* Joerg Arndt, Jun 30 2011 */
    
  • PARI
    my(x='x+O('x^30)); Vec(1/sqrt(x^6+2*x^5+x^4-2*x^3-2*x^2-4*x+1)) \\ G. C. Greubel, Apr 29 2019
    
  • Sage
    (1/sqrt(x^6+2*x^5+x^4-2*x^3-2*x^2-4*x+1)).series(x, 30).coefficients(x, sparse=False) # G. C. Greubel, Apr 29 2019

Formula

G.f.: 1/sqrt(x^6+2*x^5+x^4-2*x^3-2*x^2-4*x+1). - Mark van Hoeij, Apr 17 2013
D-finite with recurrence: n*a(n) +2*(-2*n+1)*a(n-1) +2*(-n+1)*a(n-2) +(-2*n+3)*a(n-3) +(n-2)*a(n-4) +(2*n-5)*a(n-5) +(n-3)*a(n-6)=0. - R. J. Mathar, Oct 08 2016

A192446 Number of lattice paths from (0,0) to (n,n) using steps (1,0), (3,0), (0,1), (0,3).

Original entry on oeis.org

1, 2, 6, 30, 154, 768, 3906, 20232, 105750, 556328, 2943432, 15646932, 83500126, 447057380, 2400249624, 12918250836, 69674241654, 376489511460, 2037768450480, 11045915485740, 59955446568276, 325821729044784, 1772588671356204, 9653187691115640, 52617711157401186, 287051310425050668
Offset: 0

Views

Author

Joerg Arndt, Jul 01 2011

Keywords

Comments

Diagonal of rational function 1/(1 - (x + y + x^3 + y^3)). - Gheorghe Coserea, Aug 06 2018

Crossrefs

Programs

  • Maple
    REL := 3*s^2*x^2-(1-2*s^2+2*s^3)*x-s*(s^3+2*s^2+s-1);
    ogf := sqrt((8*s^2*(x*(1-8*s^2-4*s^3)-2*s^4-4*s^3-8*s^2+2*s+3)/3-1)/(4*x^3+8*x^2+4*x-1))/(1-4*s^3);
    series(eval(ogf, s=RootOf(REL,s)),x=0,30);  # Mark van Hoeij, Apr 17 2013
    # second Maple program:
    b:= proc(x, y) option remember; `if`(y=0, 1, add((p->
          `if`(p[1]<0, 0, b(p[1], p[2])))(sort([x, y]-h)),
            h=[[1, 0], [0, 1], [3, 0], [0, 3]]))
        end:
    a:= n-> b(n$2):
    seq(a(n), n=0..30);  # Alois P. Heinz, Dec 28 2018
  • Mathematica
    a[0, 0] = 1; a[n_, k_] /; n >= 0 && k >= 0 := a[n, k] = a[n, k-1] + a[n, k-3] + a[n-1, k] + a[n-3, k]; a[, ] = 0;
    a[n_] := a[n, n];
    a /@ Range[0, 30] (* Jean-François Alcover, Oct 06 2019 *)
  • PARI
    /* same as in A092566 but use */
    steps=[[1,0], [3,0], [0,1], [0,3]];
    /* Joerg Arndt, Jun 30 2011 */
    
  • PARI
    seq(N) = {
      my(x='x + O('x^N), d=16*x^6 + 16*x^5 + 16*x^4 - 8*x^3 - 4*x^2 + 1,
         s=serreverse((1 - 2*x^2 + 2*x^3 - sqrt(d))/(6*x^2)));
      Vec(sqrt((8*s^2*(x*(1-8*s^2-4*s^3)-2*s^4-4*s^3-8*s^2+2*s+3)/3-1)/(4*x^3+8*x^2+4*x-1))/(1-4*s^3));
    };
    seq(26) \\ Gheorghe Coserea, Aug 06 2018

Formula

G.f.: sqrt((8*s^2*(x*(1-8*s^2-4*s^3)-2*s^4-4*s^3-8*s^2+2*s+3)/3-1)/(4*x^3+8*x^2+4*x-1))/(1-4*s^3) where s is a function satisfying 3*s^2*x^2-(1-2*s^2+2*s^3)*x-s*(s^3+2*s^2+s-1)=0. - Mark van Hoeij, Apr 17 2013
From Gheorghe Coserea, Aug 06 2018: (Start)
G.f. y=A(x) satisfies:
0 = (4*x^3 + 8*x^2 + 4*x - 1)^4*(108*x^3 - 108*x^2 + 36*x - 31)^2*y^8 + 4*(4*x^3 + 8*x^2 + 4*x - 1)^3*(36*x^3 + 36*x^2 - 4*x - 13)*(108*x^3 - 108*x^2 + 36*x - 31)*y^6 + 2*(4*x^3 + 8*x^2 + 4*x - 1)^2*(2160*x^6 + 4320*x^5 + 1872*x^4 - 1784*x^3 - 1576*x^2 + 472*x + 431)*y^4 + 4*(4*x^3 + 8*x^2 + 4*x - 1)*(112*x^6 + 448*x^5 + 688*x^4 + 456*x^3 + 96*x^2 + 40*x + 55)*y^2 + (4*x^3 + 12*x^2 + 12*x + 3)^2.
0 = (4*x^3 + 8*x^2 + 4*x - 1)*(108*x^3 - 108*x^2 + 36*x - 31)*(270*x^4 + 180*x^3 + 144*x^2 - 225*x - 59)*y''' + (1283040*x^9 + 1924560*x^8 + 1080864*x^7 - 1425816*x^6 - 2135376*x^5 + 33048*x^4 + 702468*x^3 + 134520*x^2 + 43892*x + 30575)*y'' + 30*(111780*x^8 + 149040*x^7 + 120960*x^6 - 122094*x^5 - 172206*x^4 - 6012*x^3 + 36615*x^2 + 10298*x - 1541)*y' + 60*(29160*x^7 + 34020*x^6 + 36288*x^5 - 43092*x^4 - 45882*x^3 - 6462*x^2 + 1890*x + 913)*y.
(End)

A201635 Triangle formed by T(n,n) = (-1)^n*Sum_{j=0..n} C(-n,j), T(n,k) = Sum_{j=0..k} T(n-1,j) for k=0..n-1, and n>=0, read by rows.

Original entry on oeis.org

1, 1, 0, 1, 1, 2, 1, 2, 4, 6, 1, 3, 7, 13, 22, 1, 4, 11, 24, 46, 80, 1, 5, 16, 40, 86, 166, 296, 1, 6, 22, 62, 148, 314, 610, 1106, 1, 7, 29, 91, 239, 553, 1163, 2269, 4166, 1, 8, 37, 128, 367, 920, 2083, 4352, 8518, 15792, 1, 9, 46, 174, 541, 1461, 3544, 7896
Offset: 0

Views

Author

Peter Luschny, Nov 14 2012

Keywords

Comments

Notation: If a sequence id is starred then the offset and/or some terms are different. Starred terms indicate the variance.
Row sums: [A026641 ] [1, 1, 4, 13, 46, 166, 610]
--
T(j+2, 2) [A000124*] [1*, 2 , 4, 7, 11, 16, 22]
T(j+3, 3) [A003600*] [1*, 2*, 6, 13, 24, 40, 62]
--
T(j , j) [A072547 ] [1, 0, 2, 6, 22, 80, 296]
T(j+1, j) [A026641 ] [1, 1, 4, 13, 46, 166, 610]
T(j+2, j) [A014300 ] [1, 2, 7, 24, 86, 314, 1163]
T(j+3, j) [A014301*] [1, 3, 11, 40, 148, 553, 2083]
T(j+4, j) [A172025 ] [1, 4, 16, 62, 239, 920, 3544]
T(j+5, j) [A172061 ] [1, 5, 22, 91, 367, 1461, 5776]
T(j+6, j) [A172062 ] [1, 6, 29, 128, 541, 2232, 9076]
T(j+7, j) [A172063 ] [1, 7, 37, 174, 771, 3300, 13820]
--
T(2j ,j) [Central ] [1, 1, 7, 40, 239, 1461, 9076]
T(2j+1,j) [A183160 ] [1, 2, 11, 62, 367, 2232, 13820]
T(2j+2,j) [ ] [1, 3, 16, 91, 541, 3300, 20476]
T(2j+3,j) [A199033*] [1, 4, 22, 128, 771, 4744, 29618]

Examples

			Triangle begins as:
[n]|k->
[0] 1
[1] 1, 0
[2] 1, 1,  2
[3] 1, 2,  4,  6
[4] 1, 3,  7, 13,  22
[5] 1, 4, 11, 24,  46,  80
[6] 1, 5, 16, 40,  86, 166, 296
[7] 1, 6, 22, 62, 148, 314, 610, 1106.
		

Programs

  • Maple
    A201635 := proc(n,k) option remember; local j;
    if n=k then (-1)^n*add(binomial(-n,j), j=0..n)
    else add(A201635(n-1,j), j=0..k) fi end:
    for n from 0 to 7 do seq(A(n,k), k=0..n) od;
  • Mathematica
    T[n_, k_]:= T[n, k]= If[k==n, (-1)^n*Sum[Binomial[-n, j], {j, 0, n}], Sum[T[n-1, j], {j, 0, k}]]; Table[T[n, k], {n,0,10}, {k,0,n}]//Flatten (* G. C. Greubel, Feb 27 2019 *)
  • PARI
    {T(n,k) = if(k==n, (-1)^n*sum(j=0,n, binomial(-n,j)), sum(j=0,k, T(n-1,j)))};
    for(n=0,10, for(k=0,n, print1(T(n,k), ", "))) \\ G. C. Greubel, Feb 27 2019
  • Sage
    @CachedFunction
    def A201635(n, k):
        if n==k: return (-1)^n*add(binomial(-n, j) for j in (0..n))
        return add(A201635(n-1, j) for j in (0..k))
    for n in (0..7) : [A201635(n, k) for k in (0..n)]
    

A226952 Triangle of coefficients of Faber polynomials for (3*x - sqrt(x^2 - 4*x))/2.

Original entry on oeis.org

0, -1, 1, -1, -2, 1, -4, 0, -3, 1, -13, -4, 2, -4, 1, -46, -10, -5, 5, -5, 1, -166, -36, -6, -8, 9, -6, 1, -610, -126, -28, 0, -14, 14, -7, 1, -2269, -456, -92, -24, 10, -24, 20, -8, 1, -8518, -1674, -333, -63, -27, 27, -39, 27, -9, 1
Offset: 0

Views

Author

Dmitry Kruchinin, Jun 24 2013

Keywords

Examples

			Triangle begins as:
    0;
   -1,   1;
   -1,  -2,  1;
   -4,   0, -3,  1;
  -13,  -4,  2, -4,  1;
  -46, -10, -5,  5, -5,  1;
		

Programs

  • Magma
    [[n eq 0 and k eq 0 select 0 else k eq n select 1 else n*(&+[ (-1)^j*j*Binomial(j+k,k)*Binomial(2*n-2*k-j-1, n-k-1)/((j+k)*(n-k)): j in [1..n-k]]): k in [0..n]]: n in [0..10]]; // G. C. Greubel, Apr 29 2019
    
  • Mathematica
    T[n_,k_]:= If[n==k==0, 0, If[k==n, 1, n*Sum[(-1)^j*j*Binomial[j+k, k]* Binomial[2*n-2*k-j-1, n-k-1]/((j+k)*(n-k)), {j, 1, n-k}]]]; Table[T[n,k], {n,0,10}, {k,0,n}]//Flatten (* G. C. Greubel, Apr 29 2019 *)
  • Maxima
    T(n,k):=if n=0 and k=0 then 0 else if n=k then 1 else n*sum(binomial(i+k,k)*(i)*binomial(2*(n-k)-i-1,n-k-1)*(-1)^(i)/((i+k)*(n-k)),i,1,n-k);
    
  • PARI
    {T(n,k) = if(n==0 && k==0, 0, if(k==n, 1, n*sum(j=1,n-k, (-1)^j*j* binomial(j+k, k)*binomial(2*n-2*k-j-1, n-k-1)/((j+k)*(n-k)))))}; \\ G. C. Greubel, Apr 29 2019
    
  • Sage
    def T(n, k):
      if (k==n==0): return 0
      elif (k==n): return 1
      else: return n*sum((-1)^j*j* binomial(j+k, k)*binomial(2*n-2*k-j-1, n-k-1)/((j+k)*(n-k)) for j in (1..n-k))
    [[T(n, k) for k in (0..n)] for n in (0..10)] # G. C. Greubel, Apr 29 2019

Formula

G.f.: log(1 + (1 - sqrt(1-4*t))/2 - t*x) = Sum_{n>0} Sum_{k=0..n} T(n,k) * x^k * t^n/n.
T(n,k) = n*Sum_{j=1..n-k} binomial(j+k,k)*(j)*binomial(2*(n-k)-j-1, n-k-1)*(-1)^j/((j+k)*(n-k)), k
(-1)^(n+1) * Sum_{k=0..n} T(n,k) = 2*A181933(n).
T(n,0) = -A026641(n-1), n>0.

A253571 Total number of even outdegree nodes among all labeled rooted trees on n nodes.

Original entry on oeis.org

1, 2, 15, 144, 1765, 26400, 466459, 9508352, 219651849, 5671088640, 161833149511, 5058050224128, 171837337744813, 6304955850432512, 248477268083174355, 10467916801317273600, 469451601966727952401, 22329535184262444220416, 1122809130124800181976575
Offset: 1

Author

Marko Riedel, Jan 03 2015

Keywords

Examples

			When n=3 there are two types of trees: rooted paths on three nodes which have one even degree node (the bottom one with zero children), giving 6*1, and trees consisting of a node with two children, of which there are 3, and they have 3 even degree nodes, giving 3*3 for a total of 6*1 + 3*3 = 15.
		

Crossrefs

Programs

  • Maple
    a:= n-> n!*coeff(series((T->(T^2+x^2)/
        (2*T*(1-T)))(-LambertW(-x)), x, n+2), x, n):
    seq(a(n), n=1..30);  # Alois P. Heinz, Jan 03 2015

Formula

E.g.f.: (T^2+z^2)/(2*T*(1-T)) where T is the labeled tree function defined by T = z exp T.

A368489 a(n) = Sum_{k=0..n} n^k * binomial(k+n,k).

Original entry on oeis.org

1, 3, 31, 643, 20421, 873806, 46994011, 3042431715, 230249448841, 19940350062394, 1944516598602711, 210829412453667998, 25156743053019602701, 3275876521195372322892, 462262670054775645538099, 70264375447526610838701091
Offset: 0

Author

Seiichi Manyama, Dec 27 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n, n^k*binomial(k+n, k));

Formula

a(n) = [x^n] 1/((1-x) * (1-n*x)^(n+1)).
a(n) ~ 4^n * n^(n - 1/2) / sqrt(Pi). - Vaclav Kotesovec, Dec 27 2023
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