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.

A123021 Triangle of coefficients of (1 - x)^n*B(x/(1 - x),n), where B(x,n) is the Morgan-Voyce polynomial related to A078812.

Original entry on oeis.org

1, 2, -1, 3, -2, 4, -2, -2, 1, 5, 0, -9, 6, -1, 6, 5, -24, 18, -4, 7, 14, -49, 36, -4, -4, 1, 8, 28, -84, 50, 20, -30, 10, -1, 9, 48, -126, 36, 115, -120, 45, -6, 10, 75, -168, -48, 358, -335, 120, -6, -6, 1, 11, 110, -198, -264, 847, -714, 175, 84, -63, 14
Offset: 0

Views

Author

Roger L. Bagula and Gary W. Adamson, Sep 24 2006

Keywords

Comments

The n-th row consists of the coefficients in the expansion of Sum_{j=0..n} A078812(n,j)*x^j*(1 - x)^(n - j).

Examples

			Triangle begins:
    1;
    2,  -1;
    3,  -2;
    4,  -2,   -2,    1;
    5,   0,   -9,    6,  -1;
    6,   5,  -24,   18,  -4;
    7,  14,  -49,   36,  -4,   -4,   1;
    8,  28,  -84,   50,  20,  -30,  10, -1;
    9,  48, -126,   36, 115, -120,  45, -6;
   10,  75, -168,  -48, 358, -335, 120, -6,  -6,  1;
   11, 110, -198, -264, 847, -714, 175, 84, -63, 14, -1;
   ... - _Franck Maminirina Ramaharo_, Oct 09 2018
		

Crossrefs

Programs

  • Mathematica
    Table[CoefficientList[Sum[Binomial[n+k+1, n-k]*x^k*(1-x)^(n-k), {k, 0, n}], x], {n, 0, 10}]//Flatten
  • Maxima
    t(n, k) := binomial(n + k + 1, n - k)$
    P(x, n) := expand(sum(t(n, j)*x^j*(1 - x)^(n - j), j, 0, n))$
    T(n, k) := ratcoef(P(x, n), x, k)$
    tabf(nn) := for n:0 thru nn do print(makelist(T(n, k), k, 0, hipow(P(x, n), x)))$ /* Franck Maminirina Ramaharo, Oct 09 2018 */
    
  • Sage
    def p(n,x): return sum( binomial(n+j+1, n-j)*x^j*(1-x)^(n-j) for j in (0..n) )
    def T(n): return ( p(n,x) ).full_simplify().coefficients(sparse=False)
    flatten([T(n) for n in (0..12)]) # G. C. Greubel, Jul 15 2021

Formula

From Franck Maminirina Ramaharo, Oct 09 2018: (Start)
Row n = coefficients in the expansion of (1/sqrt((4 - 3*x)*x))*(((2 - x + sqrt((4 - 3*x)*x))/2)^(n + 1) - ((2 - x - sqrt((4 - 3*x)*x))/2)^(n + 1)).
G.f.: 1/(1 - (2 - x)*y + (1 - x)^2*y^2).
E.g.f.: (1/sqrt((4 - 3*x)*x))*((2 - x + sqrt((4 - 3*x)*x))*exp(y*(2 - x + sqrt((4 - 3*x)*x))/2)/2 - (2 - x - sqrt((4 - 3*x)*x))*exp(y*(2 - x - sqrt((4 - 3*x)*x))/2)/2).
T(n,1) = -A254749(n+1). (End)

Extensions

Edited, new name, and offset corrected by Franck Maminirina Ramaharo, Oct 09 2018