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 1-8 of 8 results.

A295260 Array read by antidiagonals: T(n,k) = number of nonequivalent dissections of a polygon into n k-gons by nonintersecting diagonals up to rotation and reflection (k >= 3).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 1, 1, 2, 5, 4, 1, 1, 3, 8, 16, 12, 1, 1, 3, 12, 33, 60, 27, 1, 1, 4, 16, 68, 194, 261, 82, 1, 1, 4, 21, 112, 483, 1196, 1243, 228, 1, 1, 5, 27, 183, 1020, 3946, 8196, 6257, 733, 1, 1, 5, 33, 266, 1918, 10222, 34485, 58140, 32721, 2282
Offset: 1

Views

Author

Andrew Howroyd, Nov 18 2017

Keywords

Comments

The polygon prior to dissection will have n*(k-2)+2 sides.
In the Harary, Palmer and Read reference these are the sequences called h.
T(n,k) is the number of unoriented polyominoes containing n k-gonal tiles of the hyperbolic regular tiling with Schläfli symbol {k,oo}. Stereographic projections of several of these tilings on the Poincaré disk can be obtained via the Christensson link. For unoriented polyominoes, chiral pairs are counted as one. T(n,2) could represent polyominoes of the Euclidean regular tiling with Schläfli symbol {2,oo}; T(n,2) = 1. - Robert A. Russell, Jan 21 2024

Examples

			Array begins:
  ===================================================
  n\k|   3     4      5       6        7        8
  ---|-----------------------------------------------
   1 |   1     1      1       1        1        1 ...
   2 |   1     1      1       1        1        1 ...
   3 |   1     2      2       3        3        4 ...
   4 |   3     5      8      12       16       21 ...
   5 |   4    16     33      68      112      183 ...
   6 |  12    60    194     483     1020     1918 ...
   7 |  27   261   1196    3946    10222    22908 ...
   8 |  82  1243   8196   34485   109947   290511 ...
   9 | 228  6257  58140  315810  1230840  3844688 ...
  10 | 733 32721 427975 2984570 14218671 52454248 ...
  ...
		

Crossrefs

Columns k=3..7 are A000207, A005036, A005040, A004127, A005419.
Polyominoes: A295224 (oriented), A070914 (rooted).

Programs

  • Mathematica
    u[n_, k_, r_] := r*Binomial[(k - 1)*n + r, n]/((k - 1)*n + r);
    T[n_, k_] := (u[n, k, 1] + If[OddQ[n], u[(n - 1)/2, k, Quotient[k, 2]], If[OddQ[k], (u[n/2 - 1, k, k - 1] + u[n/2, k, 1])/2, u[n/2, k, 1]]] + (If[EvenQ[n], u[n/2, k, 1]] - u[n, k, 2])/2 + DivisorSum[GCD[n - 1, k], EulerPhi[#]*u[(n - 1)/#, k, k/#] &]/k)/2 /. Null -> 0;
    Table[T[n - k + 2, k + 1], {n, 1, 11}, {k, n + 1, 2, -1}] // Flatten (* Jean-François Alcover, Dec 28 2017, after Andrew Howroyd *)
  • PARI
    \\ here u is Fuss-Catalan sequence with p = k+1.
    u(n,k,r) = {r*binomial((k - 1)*n + r, n)/((k - 1)*n + r)}
    T(n,k) = {(u(n,k,1) + if(n%2, u((n-1)/2,k,k\2), if(k%2, (u(n/2-1,k,(k-1)) + u(n/2,k,1))/2, u(n/2,k,1))) + (if(n%2==0, u(n/2,k,1))-u(n,k,2))/2 + sumdiv(gcd(n-1,k), d, eulerphi(d)*u((n-1)/d,k,k/d))/k)/2}
    for(n=1, 10, for(k=3, 8, print1(T(n, k), ", ")); print);

Formula

T(n,k) ~ A295222(n,k)/(2*n) for fixed k.

A295224 Array read by antidiagonals: T(n,k) = number of nonequivalent dissections of a polygon into n k-gons by nonintersecting diagonals up to rotation (k >= 3).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 1, 1, 2, 7, 6, 1, 1, 3, 12, 25, 19, 1, 1, 3, 19, 57, 108, 49, 1, 1, 4, 26, 118, 366, 492, 150, 1, 1, 4, 35, 203, 931, 2340, 2431, 442, 1, 1, 5, 46, 332, 1989, 7756, 16252, 12371, 1424, 1, 1, 5, 57, 494, 3766, 20254, 68685, 115940, 65169, 4522
Offset: 1

Views

Author

Andrew Howroyd, Nov 17 2017

Keywords

Comments

The polygon prior to dissection will have n*(k-2)+2 sides.
In the Harary, Palmer and Read reference these are the sequences called H.
T(n,k) is the number of oriented polyominoes containing n k-gonal tiles of the hyperbolic regular tiling with Schläfli symbol {k,oo}. Stereographic projections of several of these tilings on the Poincaré disk can be obtained via the Christensson link. For oriented polyominoes, chiral pairs are counted as two. T(n,2) could represent polyominoes of the Euclidean regular tiling with Schläfli symbol {2,oo}; T(n,2) = 1. - Robert A. Russell, Jan 21 2024

Examples

			Array begins:
  =====================================================
  n\k|    3     4      5       6        7         8
  ---|-------------------------------------------------
   1 |    1     1      1       1        1         1 ...
   2 |    1     1      1       1        1         1 ...
   3 |    1     2      2       3        3         4 ...
   4 |    4     7     12      19       26        35 ...
   5 |    6    25     57     118      203       332 ...
   6 |   19   108    366     931     1989      3766 ...
   7 |   49   492   2340    7756    20254     45448 ...
   8 |  150  2431  16252   68685   219388    580203 ...
   9 |  442 12371 115940  630465  2459730   7684881 ...
  10 | 1424 65169 854981 5966610 28431861 104898024 ...
  ...
		

Crossrefs

Columns k=3..6 are A001683(n+2), A005034, A005038, A221184(n-1).
Polyominoes: A295260 (unoriented), A070914 (rooted).

Programs

  • Mathematica
    u[n_, k_, r_] := r*Binomial[(k - 1)*n + r, n]/((k - 1)*n + r);
    T[n_, k_] := u[n, k, 1] + (If[EvenQ[n], u[n/2, k, 1], 0] - u[n, k, 2])/2 + DivisorSum[GCD[n - 1, k], EulerPhi[#]*u[(n - 1)/#, k, k/#]&]/k;
    Table[T[n - k + 1, k], {n, 1, 13}, {k, n, 3, -1}] // Flatten (* Jean-François Alcover, Nov 21 2017, after Andrew Howroyd *)
  • PARI
    \\ here u is Fuss-Catalan sequence with p = k+1.
    u(n, k, r)={r*binomial((k - 1)*n + r, n)/((k - 1)*n + r)}
    T(n,k) = u(n,k,1) + (if(n%2==0, u(n/2,k,1))-u(n,k,2))/2 + sumdiv(gcd(n-1,k), d, eulerphi(d)*u((n-1)/d,k,k/d))/k;
    for(n=1, 10, for(k=3, 8, print1(T(n, k), ", ")); print);
    
  • Python
    from sympy import binomial, gcd, totient, divisors
    def u(n, k, r): return r*binomial((k - 1)*n + r, n)//((k - 1)*n + r)
    def T(n, k): return u(n, k, 1) + ((u(n//2, k, 1) if n%2==0 else 0) - u(n, k, 2))//2 + sum([totient(d)*u((n - 1)//d, k, k//d) for d in divisors(gcd(n - 1, k))])//k
    for n in range(1, 11): print([T(n, k) for k in range(3, 9)]) # Indranil Ghosh, Dec 13 2017, after PARI code

Formula

T(n,k) ~ A295222(n,k)/n for fixed k.

A295222 Array read by antidiagonals: T(n,k) is the number of nonequivalent dissections of a polygon into n k-gons by nonintersecting diagonals rooted at a cell up to rotation (k >= 3).

Original entry on oeis.org

1, 1, 1, 1, 1, 3, 1, 1, 5, 10, 1, 1, 6, 22, 30, 1, 1, 8, 40, 116, 99, 1, 1, 9, 64, 285, 612, 335, 1, 1, 11, 92, 578, 2126, 3399, 1144, 1, 1, 12, 126, 1015, 5481, 16380, 19228, 3978, 1, 1, 14, 166, 1641, 11781, 54132, 129456, 111041, 14000
Offset: 1

Views

Author

Andrew Howroyd, Nov 17 2017

Keywords

Comments

The polygon prior to dissection will have n*(k-2)+2 sides.
In the Harary, Palmer and Read reference these are the sequences called F.

Examples

			Array begins:
  ===========================================================
  n\k|     3      4       5        6         7          8
  ---|-------------------------------------------------------
   1 |     1      1       1        1         1          1 ...
   2 |     1      1       1        1         1          1 ...
   3 |     3      5       6        8         9         11 ...
   4 |    10     22      40       64        92        126 ...
   5 |    30    116     285      578      1015       1641 ...
   6 |    99    612    2126     5481     11781      22386 ...
   7 |   335   3399   16380    54132    141778     317860 ...
   8 |  1144  19228  129456   548340   1753074    4638348 ...
   9 |  3978 111041 1043460  5672645  22137570   69159400 ...
  10 | 14000 650325 8544965 59653210 284291205 1048927880 ...
  ...
		

Crossrefs

Columns k=3..5 are A003441, A005033, A005037.

Programs

  • Mathematica
    u[n_, k_, r_] := r*Binomial[(k - 1)*n + r, n]/((k - 1)*n + r);
    T[n_, k_] := DivisorSum[GCD[n-1, k], EulerPhi[#]*u[(n-1)/#, k, k/#]&]/k;
    Table[T[n - k + 3, k], {n, 1, 10}, {k, n + 2, 3, -1}] // Flatten (* Jean-François Alcover, Nov 21 2017, after Andrew Howroyd *)
  • PARI
    \\ here u is Fuss-Catalan sequence with p = k+1.
    u(n,k,r)={r*binomial((k - 1)*n + r, n)/((k - 1)*n + r)}
    T(n,k)=sumdiv(gcd(n-1,k), d, eulerphi(d)*u((n-1)/d, k, k/d))/k;
    for(n=1, 10, for(k=3, 8, print1(T(n, k), ", ")); print);
    
  • Python
    from sympy import binomial, gcd, totient, divisors
    def u(n, k, r): return r*binomial((k - 1)*n + r, n)//((k - 1)*n + r)
    def T(n, k): return sum([totient(d)*u((n - 1)//d, k, k//d) for d in divisors(gcd(n - 1, k))])//k
    for n in range(1, 11): print([T(n, k) for k in range(3, 9)]) # Indranil Ghosh, Dec 13 2017, after PARI

Formula

T(n,k) = Sum_{d|gcd(n-1,k)} phi(d)*u((n-1)/d, k, k/d)/k where u(n,k,r) = r*binomial((k - 1)*n + r, n)/((k - 1)*n + r).
T(n,k) ~ n*A070914(n,k-2)/(n*(k-2)+2) for fixed k.

A003456 Number of nonequivalent dissections of an n-gon by nonintersecting diagonals rooted at a cell up to rotation and reflection.

Original entry on oeis.org

1, 2, 5, 17, 62, 275, 1272, 6225, 31075, 158376, 816229, 4251412, 22319056, 117998524, 627573216, 3355499036, 18025442261, 97239773408, 526560862829, 2861189112867, 15595669996482, 85252072993968, 467247847612316, 2567091151780343
Offset: 3

Views

Author

Keywords

Comments

Total number of dissections of an n-gon into polygons with reflection and rooted at a cell. - Sean A. Irvine, May 14 2015

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • PARI
    \\ See A003447 for DissectionsModDihedralRooted()
    DissectionsModDihedralRooted(apply(i->1, [1..30]))

Extensions

More terms from Sean A. Irvine, May 14 2015
Name clarified by Andrew Howroyd, Nov 24 2017
a(15) corrected by Andrew Howroyd, Nov 24 2017

A370060 Array read by antidiagonals: T(n,k) is the number of achiral dissections of a polygon into n k-gons by nonintersecting diagonals rooted at a cell, n >= 1, k >= 3.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 3, 2, 1, 1, 2, 4, 2, 1, 1, 4, 4, 12, 5, 1, 1, 3, 6, 9, 18, 5, 1, 1, 5, 6, 26, 22, 55, 14, 1, 1, 4, 8, 21, 45, 52, 88, 14, 1, 1, 6, 8, 45, 51, 204, 140, 273, 42, 1, 1, 5, 10, 38, 84, 190, 380, 340, 455, 42, 1, 1, 7, 10, 69, 92, 500, 506, 1771, 969, 1428, 132
Offset: 1

Views

Author

Andrew Howroyd, Feb 08 2024

Keywords

Comments

The polygon prior to dissection will have n*(k-2)+2 sides.

Examples

			Array begins:
=============================================
n\k|  3   4   5    6    7    8    9    10 ...
---+-----------------------------------------
1  |  1   1   1    1    1    1    1     1 ...
2  |  1   1   1    1    1    1    1     1 ...
3  |  1   3   2    4    3    5    4     6 ...
4  |  2   4   4    6    6    8    8    10 ...
5  |  2  12   9   26   21   45   38    69 ...
6  |  5  18  22   45   51   84   92   135 ...
7  |  5  55  52  204  190  500  468   992 ...
8  | 14  88 140  380  506 1008 1240  2100 ...
9  | 14 273 340 1771 1950 6200 6545 15990 ...
  ...
		

Crossrefs

Columns k=3..6 are A208355(n-1), A124817(n-1), A369472, A370061.
Cf. A070914 (rooted), A295222 (oriented), A295259 (unoriented), A369929, A370062 (achiral unrooted).

Programs

  • PARI
    \\ here u is Fuss-Catalan sequence with p = k-1.
    u(n, k, r) = {r*binomial((k - 1)*n + r, n)/((k - 1)*n + r)}
    T(n, k) = {if(k%2, if(n%2, u((n-1)/2, k, (k-1)/2), u(n/2-1, k, (k-1))), if(n%2, u((n-1)/2, k, k/2+1), u(n/2-1, k, k)) )}
    for(n=1, 9, for(k=3, 10, print1(T(n, k), ", ")); print);

Formula

T(n,k) = 2*A295259(n,k) - A295222(n,k).
T(n,2*k+1) = A370062(n,2*k+1).

A003446 Number of nonequivalent dissections of a polygon into n triangles by nonintersecting diagonals rooted at a cell up to rotation and reflection.

Original entry on oeis.org

0, 1, 1, 2, 6, 16, 52, 170, 579, 1996, 7021, 24892, 89214, 321994, 1170282, 4277352, 15715249, 57999700, 214939846, 799478680, 2983699498, 11169391168, 41929537871, 157807451672, 595340479694, 2250901216266, 8527700012092, 32369067177176
Offset: 0

Views

Author

Keywords

Comments

Original name: Triangulated (n+2)-gons rooted at one of the triangles.
Also, the total number of atom-rooted polyenoids. - Sean A. Irvine, Oct 05 2015

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Column k=3 of A295259.

Programs

  • Mathematica
    c[x_] = (1 - Sqrt[1 - 4*x])/(2*x); d[x_] = 1 + x*c[x^2]; f[x_] = (x/6)*(c[x]^3 + 2*c[x^3] + 3*d[x]*c[x^2]); CoefficientList[ Series[ f[x], {x, 0, 27}], x] (* Jean-François Alcover, Sep 30 2011, after g.f. *)

Formula

Let c(x) = (1-sqrt(1-4*x))/(2*x) = g.f. for Catalan numbers (A000108), let d(x) = 1+x*c(x^2). Then g.f. is (x/6)*(c^3+2*subs(x=x^3, c)+3*d*subs(x=x^2, c)).
Recurrence: n*(n+1)*(n+2)*(12*n^10 - 396*n^9 + 5713*n^8 - 47417*n^7 + 250708*n^6 - 883176*n^5 + 2104831*n^4 - 3368071*n^3 + 3489712*n^2 - 2133004*n + 587808)*a(n) = 2*(n-1)*n*(n+1)*(24*n^10 - 756*n^9 + 10262*n^8 - 78647*n^7 + 374743*n^6 - 1154043*n^5 + 2323495*n^4 - 3057578*n^3 + 2632172*n^2 - 1456776*n + 412560)*a(n-1) + 4*(n-1)*n*(12*n^11 - 384*n^10 + 5377*n^9 - 43234*n^8 + 219811*n^7 - 731024*n^6 + 1576767*n^5 - 2055172*n^4 + 1195025*n^3 + 527398*n^2 - 1223056*n + 534240)*a(n-2) - 2*(72*n^13 - 2484*n^12 + 37950*n^11 - 339019*n^10 + 1971954*n^9 - 7887993*n^8 + 22425262*n^7 - 46437513*n^6 + 71577166*n^5 - 83189763*n^4 + 71509420*n^3 - 41716412*n^2 + 13543200*n - 1451520)*a(n-3) - 4*(n-1)*n*(2*n - 7)*(24*n^10 - 756*n^9 + 10262*n^8 - 78647*n^7 + 374743*n^6 - 1154043*n^5 + 2323495*n^4 - 3057578*n^3 + 2632172*n^2 - 1456776*n + 412560)*a(n-4) - 8*(n-1)*(2*n - 9)*(12*n^11 - 384*n^10 + 5377*n^9 - 43234*n^8 + 219811*n^7 - 731024*n^6 + 1576767*n^5 - 2055172*n^4 + 1195025*n^3 + 527398*n^2 - 1223056*n + 534240)*a(n-5) + 16*(n-6)*(2*n - 11)*(2*n - 9)*(12*n^10 - 276*n^9 + 2689*n^8 - 14529*n^7 + 48009*n^6 - 101629*n^5 + 142510*n^4 - 137838*n^3 + 93836*n^2 - 39760*n + 6720)*a(n-6). - Vaclav Kotesovec, Aug 13 2013
a(n) ~ 4^n/(2*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Aug 13 2013

Extensions

Name edited by Andrew Howroyd, Nov 20 2017

A005035 Number of nonequivalent dissections of a polygon into n quadrilaterals by nonintersecting diagonals rooted at a cell up to rotation and reflection.

Original entry on oeis.org

1, 1, 4, 13, 64, 315, 1727, 9658, 55657, 325390, 1929160, 11555172, 69840032, 425318971, 2607388905, 16077392564, 99646239355, 620439153165, 3879069845640, 24342884609625, 153279112388352, 968123122592340, 6131992590993204, 38940057166651848
Offset: 1

Views

Author

Keywords

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Column k=4 of A295259.

Programs

  • Mathematica
    u[n_, k_, r_] := r*Binomial[(k-1)*n + r, n]/((k-1)*n + r);
    F[n_, k_] := DivisorSum[GCD[n-1, k], EulerPhi[#]*u[(n-1)/#, k, k/#]&]/k;
    T[n_, k_] := (F[n, k] + If[OddQ[k], If[OddQ[n], u[(n-1)/2, k, (k-1)/2], u[n/2-1, k, k-1]], If[OddQ[n], u[(n-1)/2, k, k/2+1], u[n/2-1, k, k]]])/2;
    a[n_] := T[n, 4];
    Array[a, 24] (* Jean-François Alcover, Jul 02 2018, after Andrew Howroyd *)

Extensions

More terms from Sean A. Irvine, Mar 11 2016
Name edited by Andrew Howroyd, Nov 20 2017

A005039 Number of nonequivalent dissections of a polygon into n pentagons by nonintersecting diagonals rooted at a cell up to rotation and reflection.

Original entry on oeis.org

1, 1, 4, 22, 147, 1074, 8216, 64798, 521900, 4272967, 35447724, 297308810, 2516830890, 21476307960, 184530904560, 1595190209002, 13863857007924, 121067796450692, 1061770618201680, 9347742325179544, 82584606893075739
Offset: 1

Views

Author

Keywords

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Column k=5 of A295259.
Cf. A002293, A005037 (no mirror-image symmetries), A003446 (triangles), A005035 (quadrilaterals).

Programs

  • Mathematica
    Rest[CoefficientList[Series[x*(HypergeometricPFQ[{1/4, 1/2, 3/4}, {2/3, 4/3}, (256/27)*x]^5 + 4*HypergeometricPFQ[{1/4, 1/2, 3/4}, {2/3, 4/3}, (256/27)*x^5] + 5*HypergeometricPFQ[{1/4, 1/2, 3/4}, {2/3, 4/3}, (256/27)*x^2]^2 + 5*x*HypergeometricPFQ[{1/4, 1/2, 3/4}, {2/3, 4/3}, (256/27)*x^2]^4)/10, {x, 0, 25}], x]] (* Vaclav Kotesovec, Mar 13 2016 *)

Formula

G.f.: (1/10)*x*(u^5(x) + 4*u(x^5) + 5*u^2(x^2) + 5*x*u^4(x^2)) where u(x) is the g.f. for A002293. - Sean A. Irvine, Mar 12 2016
a(n) ~ 2^(8*n - 1/2) / (sqrt(Pi) * n^(3/2) * 3^(3*n + 5/2)). - Vaclav Kotesovec, Mar 13 2016

Extensions

More terms from Sean A. Irvine, Mar 12 2016
Name edited by Andrew Howroyd, Nov 20 2017
Showing 1-8 of 8 results.