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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A329501 Array read by upward antidiagonals: row n = coordination sequence for cylinder formed by rolling up a strip of width n squares cut from the square grid by cuts parallel to grid lines.

Original entry on oeis.org

1, 1, 2, 1, 3, 2, 1, 4, 4, 2, 1, 4, 6, 4, 2, 1, 4, 7, 6, 4, 2, 1, 4, 8, 8, 6, 4, 2, 1, 4, 8, 10, 8, 6, 4, 2, 1, 4, 8, 11, 10, 8, 6, 4, 2, 1, 4, 8, 12, 12, 10, 8, 6, 4, 2, 1, 4, 8, 12, 14, 12, 10, 8, 6, 4, 2
Offset: 1

Views

Author

N. J. A. Sloane, Nov 19 2019

Keywords

Comments

For the case when the cuts are at 45 degrees to the grid lines, see A329504.
See A329508, A329512, and A329515 for coordination sequences for cylinders formed by rolling up the hexagonal grid ("carbon nanotubes").
The g.f.s for the rows can easily be found using the "trunks and branches" method (see Goodman-Strauss and Sloane). In the illustration for n=5, there are two trunks (blue) and ten branches (red).

Examples

			Array begins:
  1, 2, 2,  2,  2,  2,  2,  2,  2,  2,  2,  2, ...
  1, 3, 4,  4,  4,  4,  4,  4,  4,  4,  4,  4, ...
  1, 4, 6,  6,  6,  6,  6,  6,  6,  6,  6,  6, ...
  1, 4, 7,  8,  8,  8,  8,  8,  8,  8,  8,  8, ...
  1, 4, 8, 10, 10, 10, 10, 10, 10, 10, 10, 10, ...
  1, 4, 8, 11, 12, 12, 12, 12, 12, 12, 12, 12, ...
  1, 4, 8, 12, 14, 14, 14, 14, 14, 14, 14, 14, ...
  1, 4, 8, 12, 15, 16, 16, 16, 16, 16, 16, 16, ...
  1, 4, 8, 12, 16, 18, 18, 18, 18, 18, 18, 18, ...
  1, 4, 8, 12, 16, 19, 20, 20, 20, 20, 20, 20, ...
  ...
The initial antidiagonals are:
  1;
  1,  2;
  1,  3,  2;
  1,  4,  4,  2;
  1,  4,  6,  4,  2;
  1,  4,  7,  6,  4,  2;
  1,  4,  8,  8,  6,  4,  2;
  1,  4,  8, 10,  8,  6,  4,  2;
  1,  4,  8, 11, 10,  8,  6,  4,  2;
  1,  4,  8, 12, 12, 10,  8,  6,  4,  2;
  1,  4,  8, 12, 14, 12, 10,  8,  6,  4,  2;
  ...
		

Crossrefs

Formula

Let theta = (1+x)/(1-x).
If n = 2*k, the g.f. for the coordination sequence for row n is theta*(1+2*x+2*x^2+...+2*x^(k-1)+x^k).
If n = 2*k+1, the g.f. for the coordination sequence for row n is theta*(1+2*x+2*x^2+...+2*x^k).

A054275 Susceptibility series H_2 for 2-dimensional Ising model (divided by 2).

Original entry on oeis.org

1, 8, 24, 52, 90, 140, 200, 272, 354, 448, 552, 668, 794, 932, 1080, 1240, 1410, 1592, 1784, 1988, 2202, 2428, 2664, 2912, 3170, 3440, 3720, 4012, 4314, 4628, 4952, 5288, 5634, 5992, 6360, 6740, 7130, 7532, 7944, 8368, 8802, 9248, 9704, 10172, 10650, 11140
Offset: 0

Views

Author

N. J. A. Sloane, May 09 2000

Keywords

Crossrefs

Programs

  • GAP
    Concatenation([1], List([1..50], n-> (22*n^2+9-(-1)^n)/4)); # G. C. Greubel, Jul 31 2019
  • Magma
    [n eq 0 select 1 else (22*n^2+9-(-1)^n)/4: n in [0..50]]; // G. C. Greubel, Jul 31 2019
    
  • Mathematica
    CoefficientList[Series[(1+6*x+8*x^2+6*x^3+x^4)/((1-x)^3*(1+x)),{x,0,50}], x] (* or *) LinearRecurrence[{2,0,-2,1},{1,8,24,52,90},51] (* Indranil Ghosh, Feb 24 2017 *)
    Table[If[n==0, 1, (22*n^2+9-(-1)^n)/4], {n,0,50}] (* G. C. Greubel, Jul 31 2019 *)
  • PARI
    Vec((1+6*x+8*x^2+6*x^3+x^4)/((1-x)^3*(1+x)) + O(x^50)) \\ Colin Barker, Dec 09 2016
    
  • PARI
    a(n)=if(n, 11*n^2+5, 2)\2 \\ Charles R Greathouse IV, Feb 24 2017
    
  • Sage
    [1]+[(22*n^2+9-(-1)^n)/4 for n in (1..50)] # G. C. Greubel, Jul 31 2019
    

Formula

G.f.: (1+6*x+8*x^2+6*x^3+x^4) / ((1-x)^3*(1+x)).
From Colin Barker, Dec 09 2016: (Start)
a(n) = (11*n^2+4)/2 for n>0 and even.
a(n) = (11*n^2+5)/2 for n odd.
a(n) = 2*a(n-1) - 2*a(n-3) + a(n-4) for n>4. (End)
E.g.f.: ((9 + 22*x + 22*x^2)*exp(x) - 4 - exp(-x))/4. - G. C. Greubel, Jul 31 2019

A054389 Susceptibility series H_5 for 2-dimensional Ising model (divided by 2).

Original entry on oeis.org

1, 20, 140, 620, 2016, 5364, 12292, 25228, 47488, 83508, 138908, 220748, 337568, 499668, 719124, 1010092, 1388800, 1873876, 2486316, 3249836, 4190816, 5338676, 6725796, 8387916, 10364032, 12696820, 15432508, 18621324, 22317344, 26578964, 31468724, 37053804
Offset: 0

Views

Author

N. J. A. Sloane, May 09 2000

Keywords

Crossrefs

Programs

  • GAP
    Concatenation([1], List([1..35], n-> n*(154*n^4 +1260*n^2 +941 -45*(-1)^n)/120)); # G. C. Greubel, Jul 31 2019
  • Magma
    [1] cat [n*(154*n^4 +1260*n^2 +941 -45*(-1)^n)/120: n in [1..35]]; // G. C. Greubel, Jul 31 2019
    
  • Mathematica
    LinearRecurrence[{4,-4,-4,10,-4,-4,4,-1}, {1,20,140,620,2016,5364,12292, 25228,47488},35] (* or *) CoefficientList[Series[(1 +16*x +64*x^2 + 144*x^3 +166*x^4 +144*x^5 +64*x^6 +16*x^7 +x^8)/((1-x)^6*(1+x)^2), {x,0, 35}], x] (* Indranil Ghosh, Feb 24 2017 *)
    Table[If[n==0, 1, n*(154*n^4 +1260*n^2 +941 -45*(-1)^n)/120], {n,0,35}] (* G. C. Greubel, Jul 31 2019 *)
  • PARI
    Vec((1 +16*x +64*x^2 +144*x^3 +166*x^4 +144*x^5 +64*x^6 +16*x^7 + x^8)/((1-x)^6*(1+x)^2) + O(x^35)) \\ Colin Barker, Dec 09 2016
    
  • Sage
    [1]+[n*(154*n^4 +1260*n^2 +941 -45*(-1)^n)/120 for n in (1..35)] # G. C. Greubel, Jul 31 2019
    

Formula

G.f.: (1 + 16*x + 64*x^2 + 144*x^3 + 166*x^4 + 144*x^5 + 64*x^6 + 16*x^7 + x^8) / ((1 - x)^6*(1 + x)^2).
From Colin Barker, Dec 09 2016: (Start)
a(n) = 4*a(n-1) - 4*a(n-2) - 4*a(n-3) + 10*a(n-4) - 4*a(n-5) - 4*a(n-6) + 4*a(n-7) - a(n-8) for n>8.
a(n) = (77*n^5 + 630*n^3 + 448*n)/60 for n>0 and even.
a(n) = (77*n^5 + 630*n^3 + 493*n)/60 for n odd. (End)
From G. C. Greubel, Jul 31 2019: (Start)
a(n) = n*(154*n^4 + 1260*n^2 + 941 - 45*(-1)^n)/120, n>0, with a(0)=1.
E.g.f.: (x*(2355 + 6090*x + 5110*x^2 + 1540*x^3 + 154*x^4)*exp(x) + 120 + 45*x*exp(-x))/120. (End)

A054410 Susceptibility series H_3 for 2-dimensional Ising model (divided by 2).

Original entry on oeis.org

1, 12, 52, 148, 328, 620, 1052, 1652, 2448, 3468, 4740, 6292, 8152, 10348, 12908, 15860, 19232, 23052, 27348, 32148, 37480, 43372, 49852, 56948, 64688, 73100, 82212, 92052, 102648, 114028, 126220, 139252, 153152, 167948, 183668, 200340, 217992, 236652
Offset: 0

Views

Author

N. J. A. Sloane, May 09 2000

Keywords

Crossrefs

Programs

  • GAP
    Concatenation([1], List([1..40], n-> 2*n*(11+7*n^2)/3)); # G. C. Greubel, Jul 31 2019
  • Magma
    [1] cat [2*n*(11+7*n^2)/3: n in [1..40]]; // G. C. Greubel, Jul 31 2019
    
  • Mathematica
    CoefficientList[Series[(1+8*x+10*x^2+8*x^3+x^4)/(1-x)^4, {x,0,40}],x] (* or *) a[0]=1; a[n_]:= 2*n*(11+7*n^2)/3; Table[a[n], {n,0,40}] (* Indranil Ghosh, Feb 24 2017 *)
    LinearRecurrence[{4,-6,4,-1},{1,12,52,148,328},50] (* Harvey P. Dale, Nov 24 2024 *)
  • PARI
    Vec((1+8*x+10*x^2+8*x^3+x^4)/(1-x)^4 + O(x^40)) \\ Colin Barker, Dec 09 2016
    
  • PARI
    vector(40, n, n--; if(n==0,1, 2*n*(11+7*n^2)/3)) \\ G. C. Greubel, Jul 31 2019
    
  • Python
    def A054410(n):
        if n == 0: return 1
        return 2*(n*(11 + 7*n**2))/3 # Indranil Ghosh, Feb 24 2017
    
  • Sage
    [1]+[2*n*(11+7*n^2)/3 for n in (1..40)] # G. C. Greubel, Jul 31 2019
    

Formula

G.f.: (1 +8*x +10*x^2 +8*x^3 +x^4)/(1-x)^4.
From Colin Barker, Dec 09 2016: (Start)
a(n) = 2*n*(11 + 7*n^2)/3 for n>0.
a(0)=1, a(1)=12, a(2)=52, a(3)=148, a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>4. (End)
E.g.f.: (3 + 2*x*(18 + 21*x + 7*x^2)*exp(x))/3. - G. C. Greubel, Jul 31 2019

A008416 Coordination sequence for 8-dimensional cubic lattice.

Original entry on oeis.org

1, 16, 128, 688, 2816, 9424, 27008, 68464, 157184, 332688, 658048, 1229360, 2187520, 3732560, 6140800, 9785072, 15158272, 22900496, 33830016, 48978352, 69629696, 97364944, 134110592, 182192752, 244396544, 324031120, 425000576
Offset: 0

Views

Author

Keywords

Comments

Coordination sequence for 8-dimensional cyclotomic lattice Z[zeta_16].

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[((1 + x)/(1 - x))^8, {x, 0, 26}], x] (* Michael De Vlieger, Dec 18 2017 *)

Formula

G.f.: ((1+x)/(1-x))^8.
a(n) = A008415(n) + A008415(n-1) + a(n-1). - Bruce J. Nicholson, Dec 17 2017
n*a(n) = 16*a(n-1) + (n-2)*a(n-2) for n > 1. - Seiichi Manyama, Jun 06 2018

A102301 a(n) = ((3*n + 1)*2^(n+3) + 9 + (-1)^n)/18.

Original entry on oeis.org

1, 4, 13, 36, 93, 228, 541, 1252, 2845, 6372, 14109, 30948, 67357, 145636, 313117, 669924, 1427229, 3029220, 6407965, 13514980, 28428061, 59652324, 124897053, 260978916, 544327453, 1133394148, 2356266781, 4891490532, 10140895005, 20997617892, 43426891549
Offset: 0

Views

Author

Creighton Dement, Feb 20 2005

Keywords

Comments

A floretion-generated sequence resulting from particular transform of A000975.
Floretion Algebra Multiplication Program, FAMP Code: 2jesforseq[ + .5'i + 'kk' + .5'jk' ], 1vesforseq(n) = A000975(n+2)*(-1)^(n+1), ForType: 1A, LoopType: tes (2nd iteration)

Crossrefs

Programs

  • Magma
    [((3*n+1)*2^(n+3)+9+(-1)^n)/18: n in [0..40]]; // Vincenzo Librandi, Nov 21 2018
  • Mathematica
    Table[((3n+1)*2^(n+3) + 9 + (-1)^n)/18, {n,0,50}] (* G. C. Greubel, Sep 27 2017 *)
    LinearRecurrence[{4, -3, -4, 4}, {1, 4, 13, 36}, 50] (* Vincenzo Librandi, Nov 21 2018 *)
  • PARI
    a(n)=((3*n+1)*2^(n+3)+9+(-1)^n)/18 \\ Charles R Greathouse IV, Oct 16 2015
    

Formula

G.f.: 1/((1-x^2)*(1-2*x)^2).
a(n+1) - 2*a(n) = A000975(n+2) (n-th number without consecutive equal binary digits)
a(n) + a(n+1) = A000337(n+2);
a(n+1) - a(n) = A045883(n+2);
a(n+2) - a(n) = A001787(n+3) ( Number of edges in n-dimensional hypercube );
a(n+2) - 2*a(n+1) + a(n) = A059570(n+3);
Convolution of "Number of fixed points in all 231-avoiding involutions in S_n" (A059570) with the natural numbers (A000027), treating the result as if offset=0. - Graeme McRae, Jul 12 2006
Equals triangle A059260 * A008574 as a vector, where A008574 = [1, 4, 8, 12, 16, 20, ...]. - Gary W. Adamson, Mar 06 2012

A180668 a(n) = a(n-1)+a(n-2)+a(n-3)+4*n-8 with a(0)=0, a(1)=0 and a(2)=1.

Original entry on oeis.org

0, 0, 1, 5, 14, 32, 67, 133, 256, 484, 905, 1681, 3110, 5740, 10579, 19481, 35856, 65976, 121377, 223277, 410702, 755432, 1389491, 2555709, 4700720, 8646012, 15902537, 29249369, 53798022, 98950036, 181997539, 334745713
Offset: 0

Views

Author

Johannes W. Meijer, Sep 21 2010

Keywords

Comments

The a(n+2) represent the Kn13 and Kn23 sums of the square array of Delannoy numbers A008288. See A180662 for the definition of these knight and other chess sums.

Crossrefs

Cf. A000073 (Kn11 & Kn21), A089068 (Kn12 & Kn22), A180668 (Kn13 & Kn23), A180669 (Kn14 & Kn24), A180670 (Kn15 & Kn25).

Programs

  • Maple
    nmax:=31: a(0):=0: a(1):=0: a(2):=1: for n from 3 to nmax do a(n):= a(n-1)+a(n-2)+a(n-3)+4*n-8 od: seq(a(n),n=0..nmax);
  • Mathematica
    LinearRecurrence[{3,-2,0,-1,1},{0,0,1,5,14},40] (* Harvey P. Dale, Dec 15 2023 *)

Formula

a(n) = a(n-1)+a(n-2)+a(n-3)+4*n-8 with a(0)=0, a(1)=0 and a(2)=1.
a(n) = a(n-1)+A001590(n+3)-2 with a(0)=0.
a(n) = sum(A008574(m)*A000073(n-m),m=0..n).
a(n+2) = add(A008288(n-k+2,k+2),k=0..floor(n/2)).
GF(x) = (x^2*(1+x)^2)/((1-x)^2*(1-x-x^2-x^3)).
Contribution from Bruno Berselli, Sep 23 2010: (Start)
a(n) = 2*a(n-1)-a(n-4)+4 for n>4.
a(n)-3*a(n-1)+2a(n-2)+a(n-4)-a(n-5) = 0 for n>4. (End)

A319840 Table read by antidiagonals: T(n, k) is the number of elements on the perimeter of an n X k matrix.

Original entry on oeis.org

1, 2, 2, 3, 4, 3, 4, 6, 6, 4, 5, 8, 8, 8, 5, 6, 10, 10, 10, 10, 6, 7, 12, 12, 12, 12, 12, 7, 8, 14, 14, 14, 14, 14, 14, 8, 9, 16, 16, 16, 16, 16, 16, 16, 9, 10, 18, 18, 18, 18, 18, 18, 18, 18, 10, 11, 20, 20, 20, 20, 20, 20, 20, 20, 20, 11, 12, 22, 22, 22
Offset: 1

Views

Author

Stefano Spezia, Sep 29 2018

Keywords

Comments

The table T(n, k) can be indifferently read by ascending or descending antidiagonals.

Examples

			The table T starts in row n=1 with columns k >= 1 as:
   1   2   3   4   5   6   7   8   9  10 ...
   2   4   6   8  10  12  14  16  18  20 ...
   3   6   8  10  12  14  16  18  20  22 ...
   4   8  10  12  14  16  18  20  22  24 ...
   5  10  12  14  16  18  20  22  24  26 ...
   6  12  14  16  18  20  22  24  26  28 ...
   7  14  16  18  20  22  24  26  28  30 ...
   8  16  18  20  22  24  26  28  30  32 ...
   9  18  20  22  24  26  28  30  32  34 ...
  10  20  22  24  26  28  30  32  34  36 ...
  ...
The triangle X(n, k) begins
  n\k|   1   2   3   4   5   6   7   8   9  10
  ---+----------------------------------------
   1 |   1
   2 |   2   2
   3 |   3   4   3
   4 |   4   6   6   4
   5 |   5   8   8   8   5
   6 |   6  10  10  10  10   6
   7 |   7  12  12  12  12  12   7
   8 |   8  14  14  14  14  14  14   8
   9 |   9  16  16  16  16  16  16  16   9
  10 |  10  18  18  18  18  18  18  18  18  10
  ...
		

Crossrefs

Cf. A000027 (1st column/right diagonal of the triangle or 1st row/column of the table), A005843 (2nd row/column of the table, or 2nd column of the triangle), A008574 (main diagonal of the table), A005893 (row sum of the triangle).
Cf. A003991 (the number of elements in an n X k matrix).

Programs

  • Magma
    [[k lt 3 or n+1-k lt 3 select (n+1-k)*k else 2*n-2: k in [1..n]]: n in [1..10]]; // triangle output
    
  • Maple
    a := (n, k) -> (n+1-k)*k-(n-1-k)*(k-2)*(limit(Heaviside(min(n+1-k, k)-3+x), x = 0, right)): seq(seq(a(n, k), k = 1 .. n), n = 1 .. 20)
  • Mathematica
    Flatten[Table[(n + 1 - k) k-(n-1-k)*(k-2)Limit[HeavisideTheta[Min[n+1-k,k]-3+x], x->0, Direction->"FromAbove"  ],{n, 20}, {k, n}]] (* or *)
    f[n_] := Table[SeriesCoefficient[(x y - x^3 y^3)/((-1 + x)^2 (-1 + y)^2), {x, 0, i + 1 - j}, {y, 0, j}], {i, n, n}, {j, 1, n}]; Flatten[Array[f,20]]
  • PARI
    T(n, k) = if ((n+1-k<3) || (k<3), (n+1-k)*k, 2*n-2);
    tabl(nn) = for(i=1, nn, for(j=1, i, print1(T(i, j), ", ")); print);
    tabl(20) \\ triangle output

Formula

T(n, k) = n*k - (n - 2)*(k - 2)*H(min(n, k) - 3), where H(x) is the Heaviside step function, taking H(0) = 1.
G.f. as rectangular array: (x*y - x^3*y^3)/((-1 + x)^2*(-1 + y)^2).
X(n, k) = A131821(n, k)*A318274(n - 1, k)*A154325(n - 1, k). - Franck Maminirina Ramaharo, Nov 18 2018

A336627 Coordination sequence for the Manhattan lattice.

Original entry on oeis.org

1, 2, 4, 8, 11, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52, 56, 60, 64, 68, 72, 76, 80, 84, 88, 92, 96, 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140, 144, 148, 152, 156, 160, 164, 168, 172, 176, 180, 184, 188, 192, 196, 200, 204, 208, 212, 216, 220, 224
Offset: 0

Views

Author

Sean A. Irvine, Jul 28 2020

Keywords

Comments

In the Manhattan lattice, N-S streets run alternately N and S, and E-W streets run alternately E and W. - N. J. A. Sloane, Jul 29 2020

Crossrefs

Cf. A008574 (square lattice), A117633 (self-avoiding walks).

Programs

  • Mathematica
    CoefficientList[Series[(1+x^2)(1+2x^3-x^4)/(1-x)^2,{x,0,80}],x] (* or *) LinearRecurrence[{2,-1},{1,2,4,8,11,16,20},80] (* Harvey P. Dale, Dec 28 2021 *)
  • PARI
    a(n)=if(n>4, 4*n-4, min(2^n, 11)) \\ Charles R Greathouse IV, Oct 18 2022

Formula

G.f.: (1+x^2) * (1+2*x^3-x^4) / (1-x)^2.
a(n) = 4*(n-1), n >= 5.

A068600 Number of n-uniform tilings having n different arrangements of polygons about their vertices.

Original entry on oeis.org

11, 20, 39, 33, 15, 10, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
Offset: 1

Views

Author

Brian Galebach, Mar 28 2002

Keywords

Comments

Sequence gives the number of edge-to-edge regular-polygon tilings having n topologically distinct vertex types, with each vertex type having a different arrangement of surrounding polygons. Does not allow for tilings with two or more vertex types having the same arrangement of surrounding polygons, even when those vertices are topologically distinct. There are no 8- or higher-uniform tilings having the equivalent number of distinct polygon arrangements.
There are eleven 1-uniform tilings (also called the "Archimedean" tessellations) which comprise the three regular tessellations (all triangles, squares, or hexagons) plus the eight semiregular tessellations. (See A250120. - N. J. A. Sloane, Nov 29 2014)

References

  • This sequence was originally calculated by Otto Krotenheerdt.
  • Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987, page 69.
  • Krotenheerdt, Otto. "Die homogenen Mosaike n-ter Ordnung in der euklidischen Ebene," Wiss. Z. Martin-Luther-Univ. Halle-Wittenberg. Math.-natur. Reihe, 18(1969), 273-290; 19 (1970)19-38 and 97-122.

Crossrefs

Cf. A068599.
List of coordination sequences for uniform planar nets: A008458 (the planar net 3.3.3.3.3.3), A008486 (6^3), A008574 (4.4.4.4 and 3.4.6.4), A008576 (4.8.8), A008579 (3.6.3.6), A008706 (3.3.3.4.4), A072154 (4.6.12), A219529 (3.3.4.3.4), A250120(3.3.3.3.6), A250122 (3.12.12).
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