Real-rooted atlas

A113214 → x ↦ x−7

Proved for all n: all roots real, in (3, 7] · alternating coefficient signs · interlacing (weak) what this means

Recurrence
\(P_{n}(x) = \left(-7 + x\right)\,P_{n-1}(x) + \left(-7 + x\right)\,P_{n-2}(x)\)
\(P_{0}(x) = 1\)
\(P_{1}(x) = -5 + x\)

Rows ?

nx0x1x2x3x4x5x6x7Pn(1)
011
1-51-4
228-11118
3-16193-171-84
4931-707194-231396
5-53905068-1853331-291-1872
631213-3498615974-3815504-3518856
7-180761235249-12876538509-6809713-411-41904

Show all 15 stored rows

Computed in your browser ?

Technical details
Node id
n-2ae85de8aa2f7a20 · revision 1 · JSON
Definition source
derived:basis_map_coefficients_of:oeis_catalog:A113214
Fingerprint
f6-03f32002a7d4b1e9

Observed on the stored rows ?

  • Degrees: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 (affine: slope 1, intercept 0)
  • Palindromic rows: no
  • γ-positive (gamma_positive): no
  • Nonnegative coefficients (nonn): no
  • Only rational roots (rr_by_factors: every nonzero row is a product of linear factors over ℚ): no

OEIS matches ?

No OEIS matches.

OEIS submission text ?

Fields to paste into an OEIS submission: the example %e, the formula %F and programs %t (Mathematica) and %o (PARI/GP) that list the same rows. For an OEIS link the row numbers, the offset and the orientation are those of the entry, as matched; the matched terms were compared with the published ones, which identifies the node with the entry on a finite prefix, not for every n. The PARI/GP program is not machine-checked here.

The atlas's own rows: n = 0, …, ascending powers of x
%e Example
Triangle begins:
  0:        1;
  1:       -5,        1;
  2:       28,      -11,        1;
  3:     -161,       93,      -17,       1;
  4:      931,     -707,      194,     -23,       1;
  5:    -5390,     5068,    -1853,     331,     -29,      1;
  6:    31213,   -34986,    15974,   -3815,     504,    -35,      1;
  7:  -180761,   235249,  -128765,   38509,   -6809,    713,    -41,    1;
  8:  1046836, -1551389,   989800, -355649,   78829, -11051,    958,  -47,   1;
  9: -6062525, 10079055, -7343385, 3081015, -821280, 144386, -16757, 1239, -53, 1;
%F Formula
The row polynomials satisfy P(n,x) = -(7-x)*P(n-1,x) - (7-x)*P(n-2,x) for n >= 2, with P(0,x) = 1, P(1,x) = -5 + x.
%t Mathematica
P[0, x_] := 1;
P[1, x_] := -5 + x;
P[n_, x_] := P[n, x] = Expand[-(7 - x)*P[n - 1, x] - (7 - x)*P[n - 2, x]];
Table[CoefficientList[P[n, x], x], {n, 0, 9}] // Flatten
%o PARI/GP
P(N) = {my(v = vector(N + 1)); v[1] = 1; v[2] = -5 + x; for(n = 2, N, my(i = n + 1); v[i] = -(7 - x)*v[i - 1] - (7 - x)*v[i - 2]); v};
row(n, p) = {my(c = Vecrev(p)); c};
T(N) = {my(v = P(N)); concat(vector(#v, i, row(i - 1, v[i])))};
T(9)

Generated with polytool c48629374597.

Proved properties

  • Real-rooted. Every row P_n, n >= 0, is zero or real-rooted with all roots in (3, 7]
    Every polynomial of the sequence has only real roots, inside the stated interval.
    by the cited steps: e-921246387fcf3a1f
  • Coefficients of one sign. Every nonzero row, n >= 0: the coefficients of P_n(-x) have one sign
    All coefficients of each polynomial have the same sign (after x -> -x when alternating).
    derived from the cited steps by a stated theorem: e-921246387fcf3a1f
  • Interlacing of consecutive rows. Rows P_(m-1), P_m interlace (weak, unordered) for every m >= 1
    The roots of consecutive polynomials alternate on the real line.
    by the cited steps: e-921246387fcf3a1f

Proof chains

1 incoming proof step. Each step is expanded back to the roots of the proof DAG, the theorem checks of a node's own rule. JSON

Used in 1 proof step

No candidate equalities or related sequences.

References

  1. [MW08] Shi-Mei Ma and Yi Wang. q-Eulerian polynomials and polynomials with only real zeros. The Electronic Journal of Combinatorics, 15(1):Research Paper 17, January 2008. doi:10.37236/741