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 1-3 of 3 results.

A383995 Series expansion of the exponential generating function exp(ff6^!(x)) - 1 where ff6^!(x) = x * (1-3*x-x^2+x^3) / (1+3*x+x^2-x^3).

Original entry on oeis.org

0, 1, -11, 61, -215, -1559, 62941, -1371131, 26310481, -474554735, 7824076741, -98881279859, -176260664711, 87457412423161, -5077434546358355, 234510433823788501, -10016559114085864799, 413333665704129673249, -16704968283664639137899, 660340818239784197391325
Offset: 0

Views

Author

Michael De Vlieger, May 16 2025

Keywords

Comments

The series ff6^!(x) is the inverse for the substitution of the series ff6(x) (given by A231690), given by the suspension of the Koszul dual of FF6. - Bérénice Delcroix-Oger, May 28 2025

Crossrefs

Programs

  • Mathematica
    nn = 19; f[x_] := Exp[x] - 1;
    Range[0, nn]! * CoefficientList[Series[f[x*(1 - 3*x - x^2 + x^3)/(1 + 3*x + x^2 - x^3)], {x, 0, nn}], x]

A231691 Cardinalities of the symmetric operad of dotted red and white trees.

Original entry on oeis.org

1, 6, 74, 1476, 41032, 1464672, 63865328, 3290120832, 195537380704, 13169097667584, 991181618539136, 82450282595311104, 7511417235983147008, 743790032122343820288, 79541198937597284060672, 9136079502141558495310848, 1121720442822518015112749056, 146607501639123412303738884096, 20322509742114322789584125210624, 2978025324234142178848508363882496
Offset: 1

Views

Author

N. J. A. Sloane, Nov 14 2013

Keywords

Examples

			A(x) = x + 6*x^2/2! + 74*x^3/3! + 1476*x^4/4! + 41032*x^5/5! + ...
		

Crossrefs

Programs

  • Maple
    S:= series(RootOf(y=-x-ln((1+x)/(1+3*x+x^2)),x),y,21):
    seq(coeff(S,y,n)*n!,n=1..21); # Robert Israel, Sep 27 2018
  • Mathematica
    terms = 20; (CoefficientList[InverseSeries[Log[x^2 + 3x + 1] - Log[1+x] - x + O[x]^(terms+1)], x]*Range[0, terms]!) // Rest (* Jean-François Alcover, Sep 16 2018, after Gheorghe Coserea *)
  • PARI
    N=21; x = 'x + O('x^N); Vec(serlaplace(serreverse(log(x^2+3*x+1) - log(1+x) - x))) \\ Gheorghe Coserea, Jan 18 2017

Formula

E.g.f. A(x) satisfies -A(x) - g(-A(x)) = x where g is the E.g.f. of A052878. - Gheorghe Coserea, Jan 18 2017, edited by Robert Israel, Sep 27 2018
a(n) ~ sqrt((5 + 7*s + 3*s^2) / (7 + 13*s + 5*s^2)) * n^(n-1) / ((log((1+3*s+s^2)/(1+s))-s)^(n - 1/2) * exp(n)), where s = A060006 - 1 = -1 + (27/2 - 3*sqrt(69)/2)^(1/3)/3 + ((9 + sqrt(69))/2)^(1/3)/3^(2/3). - Vaclav Kotesovec, Apr 21 2020

Extensions

Offset changed and more terms from Gheorghe Coserea, Jan 15 2017

A278457 Triangle T(n,k) read by rows: coefficients of polynomials P_n(t) defined in Formula section.

Original entry on oeis.org

1, 2, 2, 7, 11, 6, 30, 65, 59, 22, 143, 397, 492, 318, 90, 728, 2471, 3857, 3430, 1728, 394, 3876, 15572, 29255, 32728, 22886, 9461, 1806, 21318, 99009, 217323, 291456, 257001, 148626, 52133, 8558, 120175, 633765, 1591231, 2481597, 2622445, 1918665, 947740, 288812, 41586, 690690, 4078360, 11527318, 20467755, 25114375, 22043890, 13821764, 5964728, 1607198, 206098
Offset: 1

Views

Author

Gheorghe Coserea, Jan 15 2017

Keywords

Examples

			A(x;t) = x + (2*t+2)*x^2 + (7*t^2+11*t+6)*x^3 + (30*t^3+65*t^2+59*t+22)*x^4 + ...
Triangle starts:
n\k  [1]      [2]      [3]      [4]      [5]      [6]      [7]      [8]
[1]  1;
[2]  2,       2;
[3]  7,       11,      6;
[4]  30,      65,      59,      22;
[5]  143,     397,     492,     318,     90;
[6]  728,     2471,    3857,    3430,    1728,    394;
[7]  3876,    15572,   29255,   32728,   22886,   9461,    1806;
[8]  21318,   99009,   217323,  291456,  257001,  148626,  52133,   8558;
[9]  ...
		

Crossrefs

Column k=1 give A006013.

Programs

  • Mathematica
    Reverse[CoefficientList[#, t]]& /@ CoefficientList[InverseSeries[x ((t - 1) x^3 + (t^2 - 2t - 1) x^2 - (2t - 1) x + 1)/((1 - t) x^3 + (3 - t) x^2 + 3x + 1) + O[x]^11], x] // Flatten (* Jean-François Alcover, Sep 28 2019 *)
  • PARI
    N=11; x ='x + O('x^N);
    concat(apply(p->Vec(p), Vec(serreverse(Ser(x*((t-1)*x^3 + (t^2-2*t-1)*x^2 - (2*t-1)*x+1)/((1-t)*x^3 + (3-t)*x^2 + 3*x + 1), 'x)))))

Formula

y(x) = Sum {n>=1} P_n(t)*x^n satisfies x = y*((t-1)*y^3 + (t^2-2*t-1)*y^2 - (2*t-1)*y + 1)/((1-t)*y^3 + (3-t)*y^2 + 3*y + 1), with y(0)=0, y'(0)=1, where P_n(t) is the degree n-1 polynomial associated with row n of the triangle in order of decreasing powers of t.
P_n(0) = A006318(n-1), P_n(1) = A156017(n-1), P_n(2) = A231690(n).
Showing 1-3 of 3 results.