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.

A286781 Triangle T(n,k) read by rows: coefficients of polynomials P_n(t) defined in Formula section.

Original entry on oeis.org

1, 2, 1, 10, 9, 1, 74, 91, 23, 1, 706, 1063, 416, 46, 1, 8162, 14193, 7344, 1350, 80, 1, 110410, 213953, 134613, 34362, 3550, 127, 1, 1708394, 3602891, 2620379, 842751, 125195, 8085, 189, 1, 29752066, 67168527, 54636792, 20862684, 4009832, 382358, 16576, 268, 1, 576037442, 1375636129, 1223392968, 533394516, 124266346, 15653598, 1023340, 31356, 366, 1
Offset: 0

Views

Author

Gheorghe Coserea, May 14 2017

Keywords

Comments

T(n,k) is the number of Feynman's diagrams with k fermionic loops in the order n of the perturbative expansion in dimension zero for the self-energy function in a many-body theory of fermions with two-body interaction (see Molinari link).

Examples

			A(x;t) = 1 + (2 + t)*x + (10 + 9*t + t^2)*x^2 + (74 + 91*t + 23*t^2 + t^3)*x^3 + ...
Triangle starts:
n\k  [0]       [1]       [2]       [3]       [4]      [5]     [6]    [7]  [8]
[0]  1;
[1]  2,        1;
[2]  10,       9,        1;
[3]  74,       91,       23,       1;
[4]  706,      1063,     416,      46,       1;
[5]  8162,     14193,    7344,     1350,     80,      1;
[6]  110410,   213953,   134613,   34362,    3550,    127,    1;
[7]  1708394,  3602891,  2620379,  842751,   125195,  8085,   189,   1;
[8]  29752066, 67168527, 54636792, 20862684, 4009832, 382358, 16576, 268, 1;
[9] ...
		

Crossrefs

For vertex and polarization functions see A286782 and A286783. For GWA of the self-energy and polarization functions see A286784 and A286785.
Columns k=0-8 give: A000698(k=0), A286786(k=1), A286787(k=2), A286788(k=3), A286789(k=4), A286790(k=5), A286791(k=6), A286792(k=7), A286793(k=8).

Programs

  • Mathematica
    max = 10; y0[x_, t_] = 1; y1[x_, t_] = 0; For[n = 1, n <= max, n++, y1[x_, t_] = (1 + x*y0[x, t] + 2*x^2*D[y0[x, t], x])*(1 - x*y0[x, t]*(1 - t))/(1 - x*y0[x, t])^2 + O[x]^n // Normal; y0[x_, t_] = y1[x, t]];
    row[n_] := CoefficientList[Coefficient[y0[x, t], x, n], t];
    Table[row[n], {n, 0, max-1}] // Flatten (* Jean-François Alcover, May 19 2017, adapted from PARI *)
  • PARI
    A286781_ser(N,t='t) = {
      my(x='x+O('x^N), y0=1+O('x^N), y1=0, n=1);
      while(n++,
        y1 = (1 + x*y0 + 2*x^2*y0')*(1 - x*y0*(1-t))/(1-x*y0)^2;
        if (y1 == y0, break()); y0 = y1;);
      y0;
    };
    concat(apply(p->Vecrev(p), Vec(A286781_ser(10))))
    \\ test: y = A286781_ser(50); y*(1-x*y)^2 == (1 + x*y + 2*x^2*deriv(y,'x)) * (1 - x*y*(1-t))

Formula

y(x;t) = Sum_{n>=0} P_n(t)*x^n satisfies y * (1-x*y)^2 = (1 + x*y + 2*x^2*deriv(y,x)) * (1 - x*y*(1-t)), with y(0;t) = 1, where P_n(t) = Sum_{k=0..n} T(n,k)*t^k, 0<=n, 0<=k<=n.
A000698(n+1)=T(n,0), A101986(n)=T(n,n-1), A000108(n)=P_n(-1), A286794(n)=P_n(1).

A286788 Column 3 of A286781.

Original entry on oeis.org

1, 46, 1350, 34362, 842751, 20862684, 533394516, 14251251012, 400275122533, 11849888387786, 370032953752618, 12183464636804638, 422529226131247475, 15413172354966378040, 590459747844232859976, 23715530712277152761928, 997006212536288359365609, 43800374567467950834916070
Offset: 3

Views

Author

Gheorghe Coserea, May 16 2017

Keywords

Crossrefs

A286789 Column 4 of A286781.

Original entry on oeis.org

1, 80, 3550, 125195, 4009832, 124266346, 3854188670, 121943460540, 3979525634005, 134806148044750, 4756728585598416, 175132764223880035, 6731931366383154760, 270129431174068396380, 11308903054417009540644, 493544598057755406560688, 22431785171561428611320865
Offset: 4

Views

Author

Gheorghe Coserea, May 16 2017

Keywords

Crossrefs

A286790 Column 5 of A286781.

Original entry on oeis.org

1, 127, 8085, 382358, 15653598, 598415692, 22280470762, 828351390146, 31225895068199, 1204894853397543, 47870402081423775, 1965205314867907972, 83531844407610101388, 3679988322044604002256, 168093873703636990132596, 7960504783782783371445468
Offset: 5

Views

Author

Gheorghe Coserea, May 16 2017

Keywords

Crossrefs

A286791 Column 6 of A286781.

Original entry on oeis.org

1, 189, 16576, 1023340, 52563182, 2445890678, 108248782988, 4693939818672, 203214066766123, 8891156436472127, 396276632116578640, 18084968846773765272, 847923332620865268252, 40927316768759272656876, 2036183873275911481501656, 104482592642320957223810448
Offset: 6

Views

Author

Gheorghe Coserea, May 16 2017

Keywords

Crossrefs

A286792 Column 7 of A286781.

Original entry on oeis.org

1, 268, 31356, 2471008, 156688950, 8769288752, 457164358716, 22959079494036, 1135195898868631, 56066461542293032, 2793059847097230456, 141275485011659499936, 7287917154352619470284, 384587934464798917826784, 20802129691800205763744280, 1154767942465769017202459544
Offset: 7

Views

Author

Gheorghe Coserea, May 16 2017

Keywords

Crossrefs

A286793 Column 8 of A286781.

Original entry on oeis.org

1, 366, 55650, 5493004, 423998498, 28236562692, 1719625254528, 99364697625603, 5581585635090040, 309848573192308938, 17191725056094651066, 960908576231662848594, 54403314773991195041214, 3132006013784614723699158, 183841318769012678798846646, 11022935912713058281592718756
Offset: 8

Views

Author

Gheorghe Coserea, May 16 2017

Keywords

Crossrefs

A287031 Column 1 of A286782.

Original entry on oeis.org

3, 45, 637, 9567, 156123, 2781389, 54043365, 1141864959, 26137086451, 645573913005, 17138071687053, 487130581207775, 14771502665168715, 476244289169954253, 16274079501768450421, 587711952558035789055, 22370368544174736836835, 895269564785985107345453, 37585737112233443277746589
Offset: 2

Views

Author

Gheorghe Coserea, May 18 2017

Keywords

Crossrefs

Cf. A286782.

Programs

  • PARI
    A286781_ser(N, t='t) = {
      my(x='x+O('x^N), y0=1+O('x^N), y1=0, n=1);
      while(n++,
        y1 = (1 + x*y0 + 2*x^2*y0')*(1 - x*y0*(1-t))/(1-x*y0)^2;
        if (y1 == y0, break()); y0 = y1; );
      y0;
    };
    A286782_ser(N, t='t) = my(s=A286781_ser(N, t)); 1 + x*s + 2*x^2 * deriv(s,'x);
    Kol(K, N=20) = {
      my(v = A286782_ser(N+K+1, 't+O('t^(K+1))));
      vector(N, n, polcoeff(polcoeff(v, K+n), K));
    };
    Kol(1)

Formula

a(n) = (2*n-1)*A286786(n-1).
Showing 1-8 of 8 results.