narayana → basis A013610

nonnegative coefficients

Proved for all n: all roots real, in (−∞, 0] · coefficients of one sign · interlacing (weak) · Hadamard kernel what this means

Recurrence

\(\left(1 + n\right)\,P_{n}(x) = \left(18\,x^{2} - 9\,n x^{2}\right)\,P_{n-2}(x) + \left(-2 - 3\,x + 4\,n + 6\,n x\right)\,P_{n-1}(x)\)

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

\(P_{2}(x) = 2 + 3\,x\)

Rows ?

n	x⁰	x¹	x²	x³	x⁴	x⁵	x⁶	x⁷	P_n(1)
1	1								1
2	2	3							5
3	5	15	9						29
4	14	63	81	27					185
5	42	252	504	378	81				1257
6	132	990	2700	3240	1620	243			8925
7	429	3861	13365	22275	18225	6561	729		65445
8	1430	15015	63063	135135	155925	93555	25515	2187	491825

Show all 15 stored rows

Computed in your browser ?

Technical details

Node id: n-9c4b1c1c0d7d0597 · revision 1 · JSON
Definition source: derived:basis_map_A013610
Fingerprint: f6-cb4056e025ca2479

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 -1)
Palindromic rows: no
γ-positive (gamma_positive): no
Nonnegative coefficients (nonn): yes
Only rational roots (rr_by_factors: every nonzero row is a product of linear factors over ℚ): no

OEIS matches ?

A127846: row sums, 15 terms agree OEIS nonn (row-sum match: finite agreement only) · view at the OEIS
A059231: row sums, 15 terms agree OEIS nonn (row-sum match: finite agreement only) · view at the OEIS

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 = 1, …, ascending powers of x

%e Example

Triangle begins:
   1:     1;
   2:     2,      3;
   3:     5,     15,       9;
   4:    14,     63,      81,      27;
   5:    42,    252,     504,     378,      81;
   6:   132,    990,    2700,    3240,    1620,     243;
   7:   429,   3861,   13365,   22275,   18225,    6561,     729;
   8:  1430,  15015,   63063,  135135,  155925,   93555,   25515,    2187;
   9:  4862,  58344,  288288,  756756, 1135134,  972972,  449064,   96228,   6561;
  10: 16796, 226746, 1288872, 4009824, 7429968, 8358714, 5572476, 2047032, 354294, 19683;

%F Formula

The row polynomials satisfy (n+1)*P(n,x) = -(9*n-18)*x^2*P(n-2,x) + (4*n-2+(6*n-3)*x)*P(n-1,x) for n >= 3, with P(1,x) = 1, P(2,x) = 2 + 3*x.

%t Mathematica

P[1, x_] := 1;
P[2, x_] := 2 + 3*x;
P[n_, x_] := P[n, x] = Expand[Together[(-(9*n - 18)*x^2*P[n - 2, x] + (4*n - 2 + (6*n - 3)*x)*P[n - 1, x])/(n + 1)]];
Table[CoefficientList[P[n, x], x], {n, 1, 10}] // Flatten

%o PARI/GP

P(N) = {my(v = vector(N)); v[1] = 1; v[2] = 2 + 3*x; for(n = 3, N, my(i = n); v[i] = (-(9*n - 18)*x^2*v[i - 2] + (4*n - 2 + (6*n - 3)*x)*v[i - 1])/(n + 1)); v};
row(n, p) = {my(c = Vecrev(p)); c};
T(N) = {my(v = P(N)); concat(vector(#v, i, row(i, v[i])))};
T(10)

Generated with polytool c48629374597.

Proved properties

Real-rooted. Every row P_n, n >= 1, is zero or real-rooted with all roots in (-inf, 0]
Every polynomial of the sequence has only real roots, inside the stated interval.

by the cited steps: e-21b441a6a6a148f7
Coefficients of one sign. Every nonzero row, n >= 1: the coefficients of P_n 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-21b441a6a6a148f7
Hadamard kernel (Malo). Rows P_n, n >= 1, are Hadamard kernels (preserve real-rootedness)
Multiplying the coefficients of any real-rooted polynomial termwise by those of a row (Hadamard product) gives a real-rooted polynomial again.

derived from the cited steps by a stated theorem: e-21b441a6a6a148f7
Interlacing of consecutive rows. Rows P_(m-1), P_m interlace (weak, unordered) for every m >= 2
The roots of consecutive polynomials alternate on the real line.

by the cited steps: e-21b441a6a6a148f7

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

basis_map A013610 e-21b441a6a6a148f7

Geometric basis map (elementary) polytool ?
- premise (sequence): narayana
  uses: Every row P_n, n >= 1, is zero or real-rooted with all roots in (-inf, 0]
  - theorem_check three_term_recurrence e-46a461774e271ec3 root: theorem check
    
    Three-term recurrence criterion [Sze39, §3.3; Fav35] polytool ?
  - preserver_image reversal, shift 0 e-29ef477df4172e22
    
    Affine, reversal and Möbius substitutions (elementary) polytool ?
    
    premise (sequence): narayana
    uses: Every row P_n, n >= 1, is zero or real-rooted with all roots in (-inf, 0]
    
    ↵ theorem_check three_term_recurrence e-46a461774e271ec3 (expanded above)

Related sequences ?

Same fingerprint (1)

Equal up to content, sign, reversal and a small index shift.

A001263 → basis A013610

References

[Fav35] Jean Favard. Sur les polynômes de tchebicheff. C. R. Acad. Sci. Paris, 200:2052–2053, 1935.
[Sze39] G. Szegő. Orthogonal Polynomials. Colloquium publications, American Mathematical Society, 1939. doi:10.1090/coll/023