A099093 → x ↦ x−7

Proved for all n: all roots real, in (17/3, 7] · alternating coefficient signs · interlacing (weak) what this means

Recurrence

\(P_{n}(x) = \left(-21 + 3\,x\right)\,P_{n-1}(x) + \left(-21 + 3\,x\right)\,P_{n-2}(x)\)

\(P_{0}(x) = 1\)

\(P_{1}(x) = -21 + 3\,x\)

Rows ?

n	x⁰	x¹	x²	x³	x⁴	x⁵	x⁶	x⁷	P_n(1)
0	1								1
1	-21	3							-18
2	420	-123	9						306
3	-8379	3717	-549	27					-5184
4	167139	-99351	22122	-2187	81				87804
5	-3333960	2484594	-739935	110079	-8181	243			-1487160
6	66503241	-59590566	22229802	-4419171	493776	-29403	729		25188408
7	-1326554901	1388733255	-622605123	154960533	-23124771	2069145	-102789	2187	-426622464

Show all 15 stored rows

Computed in your browser ?

Technical details

Node id: n-b481f693dcd8357c · revision 1 · JSON
Definition source: derived:basis_map_coefficients_of:oeis_catalog:A099093
Fingerprint: f6-9160cb87e92f9c3a

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:           -21,            3;
  2:           420,         -123,             9;
  3:         -8379,         3717,          -549,           27;
  4:        167139,       -99351,         22122,        -2187,           81;
  5:      -3333960,      2484594,       -739935,       110079,        -8181,        243;
  6:      66503241,    -59590566,      22229802,     -4419171,       493776,     -29403,        729;
  7:   -1326554901,   1388733255,    -622605123,    154960533,    -23124771,    2069145,    -102789,     2187;
  8:   26461084860, -31692151449,   16595309808,  -4962494565,    926874981, -110727567,    8262486,  -352107,     6561;
  9: -527825129139, 711775371951, -426337052967, 148876328727, -33401356506, 4993077492, -497328903, 31827411, -1187541, 19683;

%F Formula

The row polynomials satisfy P(n,x) = -(21-3*x)*P(n-1,x) - (21-3*x)*P(n-2,x) for n >= 2, with P(0,x) = 1, P(1,x) = -21 + 3*x.

%t Mathematica

P[0, x_] := 1;
P[1, x_] := -21 + 3*x;
P[n_, x_] := P[n, x] = Expand[-(21 - 3*x)*P[n - 1, x] - (21 - 3*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] = -21 + 3*x; for(n = 2, N, my(i = n + 1); v[i] = -(21 - 3*x)*v[i - 1] - (21 - 3*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 (17/3, 7]
Every polynomial of the sequence has only real roots, inside the stated interval.

by the cited steps: e-bc143c20b95292bc
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-bc143c20b95292bc
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-bc143c20b95292bc

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

preserver_image affine, shift 0 e-bc143c20b95292bc

Affine, reversal and Möbius substitutions (elementary) polytool ?
- premise (sequence): Riordan array (1, 3+3x).
  uses: Every row P_n, n >= 0, is zero or real-rooted with all roots in (-4/3, 0]
  - theorem_check ma_wang_interval e-a3711e6f8037cbc8 root: theorem check
    
    Ma–Wang interval theorem [MW08, Thm 2, Cor 3] RealRooted RealRooted.affineEndpointStep_closed ?

Used in 1 proof step

e-04516916870a85c6 basis_map (A027466) → Riordan array (1, 3+3x).

Related sequences ?

No candidate equalities or related sequences.

References

[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