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.

A367210 Triangular array T(n,k), read by rows: coefficients of strong divisibility sequence of polynomials p(1,x) = 1, p(2,x) = 1 + 5x, p(n,x) = u*p(n-1,x) + v*p(n-2,x) for n >=3, where u = p(2,x), v = 1 - x - x^2.

Original entry on oeis.org

1, 1, 5, 2, 9, 24, 3, 23, 63, 115, 5, 45, 191, 397, 551, 8, 90, 453, 1381, 2358, 2640, 13, 170, 1044, 3807, 9226, 13482, 12649, 21, 317, 2249, 9865, 28785, 58513, 75061, 60605, 34, 579, 4695, 23703, 82485, 202887, 357567, 409779, 290376, 55, 1045, 9501
Offset: 1

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Author

Clark Kimberling, Nov 13 2023

Keywords

Comments

Because (p(n,x)) is a strong divisibility sequence, for each integer k, the sequence (p(n,k)) is a strong divisibility sequence of integers.

Examples

			First eight rows:
 1
 1    5
 2    9    24
 3   23    63   115
 5   45   191   397    551
 8   90   453  1381   2358   2640
13  170  1044  3807   9226  13482  12649
21  317  2249  9865  28785  58513  75061  60605
Row 4 represents the polynomial p(4,x) = 3 + 23 x + 63 x^2 + 115 x^3, so  that (T(4,k)) = (3,23,63,115), k-0..3.
		

Crossrefs

Cf. A000045 (column 1), A004254 (T(n,n-1)), A001109 (row sums p(n,1)), A001076 (alternating row sums, p(n,-1)), A094440, A367208, A367209, A367211, A367297, A367298, A367299, A367300.

Programs

  • Mathematica
    p[1, x_] := 1; p[2, x_] := 1 + 5 x; u[x_] := p[2, x]; v[x_] := 1 - x - x^2;
    p[n_, x_] := Expand[u[x]*p[n - 1, x] + v[x]*p[n - 2, x]]
    Grid[Table[CoefficientList[p[n, x], x], {n, 1, 10}]]
    Flatten[Table[CoefficientList[p[n, x], x], {n, 1, 10}]]

Formula

p(n,x) = u*p(n-1,x) + v*p(n-2,x) for n >=3, where p(1,x) = 1, p(2,x) = 1 + 5x, u = p(2,x), and v = 1 - x - x^2.
p(n,x) = k*(b^n - c^n), where k = -(1/D), b = 1/2 (1 + 5 x - D), c = 1/2 (1 + 5 x + D), where D = sqrt(5 + 6 x + 21 x^2).