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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A274882 a(n) is the largest coefficient of q-binomial(2*n, n) / q-binomial(n+1, 1), which are the q-Catalan polynomials.

Original entry on oeis.org

1, 1, 1, 1, 2, 4, 9, 23, 62, 176, 512, 1551, 4822, 15266, 49141, 160728, 532890, 1785162, 6039328, 20617808, 70951548, 245911020, 857888714, 3010811846, 10624583264, 37680980256, 134260382400, 480440869030, 1726092837412, 6224442777366, 22523780202156
Offset: 0

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Author

Peter Luschny, Jul 19 2016

Keywords

Crossrefs

Cf. A000108, A129175 (coefficients of q_Catalan polynomials), A275213.

Programs

  • Maple
    with(QDifferenceEquations): MaxQCatalan := proc(n) local P; P := f -> expand(simplify(expand(f))); P(QBinomial(2*n,n,q)/QBrackets(n+1,q)); max(seq(coeff(%,q,j), j=0..degree(%))) end: seq(MaxQCatalan(n), n=0..20);
  • Mathematica
    p[n_] := QBinomial[2n,n,q]/QBinomial[n+1,1,q]; Table[Max[CoefficientList[p[n] // FunctionExpand, q]], {n,0,20}] // Flatten
  • Sage
    from sage.combinat.q_analogues import q_catalan_number
    def T(n): return q_catalan_number(n)
    print([max(T(n)) for n in (0..10)])

Formula

Conjecture: a(n) ~ sqrt(3) * 2^(2*n) / (Pi * n^3). - Vaclav Kotesovec, Jan 06 2023
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