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 1-6 of 6 results.

A343092 Triangle read by rows: T(n,k) is the number of rooted toroidal maps with n edges and k faces and without isthmuses, n >= 2, k = 1..n-1.

Original entry on oeis.org

1, 4, 10, 10, 79, 70, 20, 340, 900, 420, 35, 1071, 5846, 7885, 2310, 56, 2772, 26320, 71372, 59080, 12012, 84, 6258, 93436, 431739, 706068, 398846, 60060, 120, 12768, 280120, 2000280, 5494896, 6052840, 2499096, 291720, 165, 24090, 739420, 7643265, 32055391, 58677420, 46759630, 14805705, 1385670
Offset: 2

Views

Author

Andrew Howroyd, Apr 04 2021

Keywords

Comments

The number of vertices is n - k.
Column k is a polynomial of degree 3*k. This is because adding a face can increase the number of vertices whose degree is greater than two by at most two.

Examples

			Triangle begins:
   1;
   4,   10;
  10,   79,    70;
  20,  340,   900,    420;
  35, 1071,  5846,   7885,   2310;
  56, 2772, 26320,  71372,  59080,  12012;
  84, 6258, 93436, 431739, 706068, 398846, 60060;
  ...
		

Crossrefs

Columns 1..2 are A000292, A006469.
Diagonals are A002802, A006425, A006426, A006427.
Row sums are A343093.

Programs

  • PARI
    \\ Needs F from A342989.
    G(n,m,y,z)={my(p=F(n,m,y,z)); subst(p, x, serreverse(x*p^2))}
    H(n, g=1)={my(q=G(n, g, 'y, 'z)-x, v=Vec(polcoef(sqrt(serreverse(x/q^2)/x), g, 'y))); [Vecrev(t) | t<-v]}
    { my(T=H(10)); for(n=1, #T, print(T[n])) }

A343090 Triangle read by rows: T(n,k) is the number of rooted toroidal maps with n edges and k faces and without separating cycles or isthmuses, n >= 2, k = 1..n-1.

Original entry on oeis.org

1, 4, 4, 10, 47, 10, 20, 240, 240, 20, 35, 831, 2246, 831, 35, 56, 2282, 12656, 12656, 2282, 56, 84, 5362, 52164, 109075, 52164, 5362, 84, 120, 11256, 173776, 648792, 648792, 173776, 11256, 120, 165, 21690, 495820, 2978245, 5360286, 2978245, 495820, 21690, 165
Offset: 2

Views

Author

Andrew Howroyd, Apr 04 2021

Keywords

Comments

The number of vertices is n-k.
Column k is a polynomial of degree 3*k. This is because adding a face can increase the number of vertices whose degree is greater than two by at most two.

Examples

			Triangle begins:
    1;
    4,     4;
   10,    47,     10;
   20,   240,    240,     20;
   35,   831,   2246,    831,     35;
   56,  2282,  12656,  12656,   2282,     56;
   84,  5362,  52164, 109075,  52164,   5362,    84;
  120, 11256, 173776, 648792, 648792, 173776, 11256, 120;
  ...
		

Crossrefs

Columns 1..4 are A000292, A006422, A006423, A006424.
Row sums are A343091.

Programs

  • PARI
    \\ Needs F from A342989.
    G(n,m,y,z)={my(p=F(n,m,y,z)); subst(p, x, serreverse(x*p^2))}
    H(n, g=1)={my(q=G(n, g, 'y, 'z)-x*(1+'z), v=Vec(polcoef(sqrt(serreverse(x/q^2)/x), g, 'y))); [Vecrev(t) | t<-v]}
    { my(T=H(10)); for(n=1, #T, print(T[n])) }

Formula

T(n,n-k) = T(n,k).

A006408 Number of nonseparable rooted toroidal maps with n + 3 edges and n + 1 vertices.

Original entry on oeis.org

4, 39, 190, 651, 1792, 4242, 8988, 17490, 31812, 54769, 90090, 142597, 218400, 325108, 472056, 670548, 934116, 1278795, 1723414, 2289903, 3003616, 3893670, 4993300, 6340230, 7977060, 9951669, 12317634, 15134665, 18469056, 22394152, 26990832, 32348008, 38563140
Offset: 2

Views

Author

Keywords

Comments

The number of faces is 2. - Andrew Howroyd, Apr 05 2021

References

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

Crossrefs

Column 2 of A342989.

Programs

  • PARI
    a(n) = {binomial(n+2,4)*(8*n^2 + 17*n - 6)/15} \\ Andrew Howroyd, Apr 05 2021

Formula

From Colin Barker, Apr 08 2013: (Start)
a(n) = (n*(12-28*n-45*n^2+20*n^3+33*n^4+8*n^5))/360.
G.f.: -x^2*(x^2 + 11*x + 4) / (x-1)^7. (End)
a(n) = binomial(n+2,4)*(8*n^2 + 17*n - 6)/15. - Andrew Howroyd, Apr 05 2021

Extensions

Title improved by Sean A. Irvine, Apr 03 2017
Terms a(11) and beyond from Andrew Howroyd, Apr 05 2021

A006409 Number of nonseparable rooted toroidal maps with n + 4 edges and n + 1 vertices.

Original entry on oeis.org

10, 190, 1568, 8344, 33580, 111100, 317680, 811096, 1891318, 4094090, 8328320, 16071120, 29636984, 52540472, 89974880, 149432720, 241497410, 380839382, 587453856, 888181800, 1318560100, 1925051700, 2767711440, 3923348520, 5489251950, 7587551010, 10370288640
Offset: 2

Views

Author

Keywords

Comments

The number of faces is 3. - Andrew Howroyd, Apr 05 2021

References

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

Crossrefs

Column 3 of A342989.

Programs

  • PARI
    a(n) = {binomial(n + 4, 6)*(29*n^3 + 108*n^2 - 11*n - 12)/63} \\ Andrew Howroyd, Apr 05 2021

Formula

a(n) = 10 * binomial(n + 4, 6) + 120 * binomial(n + 4, 7) + 328 * binomial(n + 4, 8) + 232 * binomial(n + 4, 9) [From Walsh]. - Sean A. Irvine, Apr 03 2017
a(n) = binomial(n + 4, 6)*(29*n^3 + 108*n^2 - 11*n - 12)/63. - Andrew Howroyd, Apr 05 2021

Extensions

Terms a(10) and beyond from Andrew Howroyd, Apr 05 2021

A006410 Number of nonseparable rooted toroidal maps with n + 5 edges and n + 1 vertices.

Original entry on oeis.org

20, 651, 8344, 64667, 361884, 1607125, 5997992, 19535997, 57014776, 151986562, 375470160, 869285378, 1902886024, 3966657702, 7920130544, 15220758070, 28268206764, 50910912965, 89176474920, 152305796565, 254193384900, 415363487955, 665644575960, 1047743815755
Offset: 2

Views

Author

Keywords

Comments

The number of faces is 4. - Andrew Howroyd, Apr 05 2021

References

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

Crossrefs

Column 4 of A342989.

Programs

  • PARI
    a(n) = {binomial(n + 6, 8)*(136*n^4 + 790*n^3 + 447*n^2 - 180*n - 24)/495} \\ Andrew Howroyd, Apr 05 2021

Formula

a(n) = 20 * binomial(n + 6, 8) + 471 * binomial(n + 6, 9) + 2734 * binomial(n + 6, 10) + 5388 * binomial(n + 6, 11) + 3264 * binomial(n + 6, 12) [From Walsh]. - Sean A. Irvine, Apr 03 2017
a(n) = binomial(n + 6, 8)*(136*n^4 + 790*n^3 + 447*n^2 - 180*n - 24)/495. - Andrew Howroyd, Apr 05 2021

Extensions

Terms a(9) and beyond from Andrew Howroyd, Apr 05 2021

A343089 Number of nonseparable rooted toroidal maps with n edges.

Original entry on oeis.org

1, 8, 59, 420, 2940, 20384, 140479, 964184, 6598481, 45059872, 307197620, 2091615760, 14226362200, 96680047568, 656559634503, 4456100344560, 30228597199443, 204971912361512, 1389342336011059, 9414200925647540, 63772600432265968, 431892497914345472
Offset: 2

Views

Author

Andrew Howroyd, Apr 04 2021

Keywords

Crossrefs

Row sums of A342989.
Cf. A006300.
Showing 1-6 of 6 results.