Real-rooted atlas

A119900: Triangle read by rows: T(n,k) is the number of binary words of length n with k strictly increasing runs, for 0<=k<=n.

A119900 ↗ nonnegative coefficients

Proved for all n all roots real, in (−∞, 0]coefficients of one signHadamard kernel

Recurrence from A119900

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

Rows ?

nx0x1x2x3x4x5x6x7Pn(1)
011
1022
20134
300448
400110516
5000620632
600012135764
70000856568128

All 15 rows b-files: A000079 (row sums), A034867 (reversed triangle), A109447, A119900, A202064 (reversed triangle) ?

Technical details
Node id
n-e8e64448d4c6498a · revision 0 · JSON
Definition source
oeis_catalog:A119900
Fingerprint
f6-937db0732045a112

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): yes
  • Only rational roots (rr_by_factors: every nonzero row is a product of linear factors over ℚ): no

Matches ?

  • A202064 reversed triangle 66 terms, 11 rows · tabl · nonn · catalog b-file?
  • A109447 triangle 64 terms, 15 rows · tabf · nonn · catalog b-file?
  • A119900 triangle 86 terms, 12 rows · tabl · nonn · catalog b-file?
  • A034867 reversed triangle 64 terms, 15 rows · tabf · nonn · catalog b-file?

Row sums ? A050732, A000079, A011782, A034008, A220051, A166444, A118655, A131577

Submission text ?

Atlas rows n = 0, …, ascending powers of x
%e Example
Triangle begins:
  0: 1;
  1: 0, 2;
  2: 0, 1, 3;
  3: 0, 0, 4,  4;
  4: 0, 0, 1, 10,  5;
  5: 0, 0, 0,  6, 20,  6;
  6: 0, 0, 0,  1, 21, 35,   7;
  7: 0, 0, 0,  0,  8, 56,  56,   8;
  8: 0, 0, 0,  0,  1, 36, 126,  84,   9;
  9: 0, 0, 0,  0,  0, 10, 120, 252, 120, 10;
%F Formula
The row polynomials satisfy P(n,x) = 2*x*P(n-1,x) + (x-x^2)*P(n-2,x) for n >= 2, with P(0,x) = 1, P(1,x) = 2*x.
%t Mathematica
P[0, x_] := 1;
P[1, x_] := 2*x;
P[n_, x_] := P[n, x] = Expand[2*x*P[n - 1, x] + (x - x^2)*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] = 2*x; for(n = 2, N, my(i = n + 1); v[i] = 2*x*v[i - 1] + (x - x^2)*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)

polytool c48629374597

A034867 reversed triangle, offset 0, from P0, low zeros dropped
%e Example
Triangle begins:
  0:  1;
  1:  2;
  2:  3,   1;
  3:  4,   4;
  4:  5,  10,   1;
  5:  6,  20,   6;
  6:  7,  35,  21,   1;
  7:  8,  56,  56,   8;
  8:  9,  84, 126,  36,  1;
  9: 10, 120, 252, 120, 10;
%F Formula
Row n lists the coefficients of P(n,x) in descending powers of x, down to the lowest nonzero coefficient, where P(n,x) = 2*x*P(n-1,x) + (x-x^2)*P(n-2,x) for n >= 2, with P(0,x) = 1, P(1,x) = 2*x.
%t Mathematica
P[0, x_] := 1;
P[1, x_] := 2*x;
P[n_, x_] := P[n, x] = Expand[2*x*P[n - 1, x] + (x - x^2)*P[n - 2, x]];
Table[Reverse[CoefficientList[Expand[P[n, x]/x^Exponent[P[n, x], x, Min]], x]], {n, 0, 9}] // Flatten
%o PARI/GP
P(N) = {my(v = vector(N + 1)); v[1] = 1; v[2] = 2*x; for(n = 2, N, my(i = n + 1); v[i] = 2*x*v[i - 1] + (x - x^2)*v[i - 2]); v};
row(n, p) = {my(c = Vecrev(p/x^valuation(p, x))); c = Vecrev(c); c};
T(N) = {my(v = P(N)); concat(vector(#v, i, row(i - 1, v[i])))};
T(9)

polytool c48629374597

A109447 triangle, offset 1, from P0, low zeros dropped
%e Example
Triangle begins:
   1:  1;
   2:  2;
   3:  1,   3;
   4:  4,   4;
   5:  1,  10,   5;
   6:  6,  20,   6;
   7:  1,  21,  35,   7;
   8:  8,  56,  56,   8;
   9:  1,  36, 126,  84,  9;
  10: 10, 120, 252, 120, 10;
%F Formula
Row n lists the coefficients of P(n,x) in ascending powers of x, starting at the lowest nonzero coefficient, where P(n,x) = 2*x*P(n-1,x) + (x-x^2)*P(n-2,x) for n >= 3, with P(1,x) = 1, P(2,x) = 2*x.
%t Mathematica
P[1, x_] := 1;
P[2, x_] := 2*x;
P[n_, x_] := P[n, x] = Expand[2*x*P[n - 1, x] + (x - x^2)*P[n - 2, x]];
Table[CoefficientList[Expand[P[n, x]/x^Exponent[P[n, x], x, Min]], x], {n, 1, 10}] // Flatten
%o PARI/GP
P(N) = {my(v = vector(N)); v[1] = 1; v[2] = 2*x; for(n = 3, N, my(i = n); v[i] = 2*x*v[i - 1] + (x - x^2)*v[i - 2]); v};
row(n, p) = {my(c = Vecrev(p/x^valuation(p, x))); c};
T(N) = {my(v = P(N)); concat(vector(#v, i, row(i, v[i])))};
T(10)

polytool c48629374597

A119900 triangle, offset 0, from P0
%e Example
Triangle begins:
  0: 1;
  1: 0, 2;
  2: 0, 1, 3;
  3: 0, 0, 4,  4;
  4: 0, 0, 1, 10,  5;
  5: 0, 0, 0,  6, 20,  6;
  6: 0, 0, 0,  1, 21, 35,   7;
  7: 0, 0, 0,  0,  8, 56,  56,   8;
  8: 0, 0, 0,  0,  1, 36, 126,  84,   9;
  9: 0, 0, 0,  0,  0, 10, 120, 252, 120, 10;
%F Formula
The row polynomials satisfy P(n,x) = 2*x*P(n-1,x) + (x-x^2)*P(n-2,x) for n >= 2, with P(0,x) = 1, P(1,x) = 2*x.
%t Mathematica
P[0, x_] := 1;
P[1, x_] := 2*x;
P[n_, x_] := P[n, x] = Expand[2*x*P[n - 1, x] + (x - x^2)*P[n - 2, x]];
Table[PadRight[CoefficientList[P[n, x], x], n + 1], {n, 0, 9}] // Flatten
%o PARI/GP
P(N) = {my(v = vector(N + 1)); v[1] = 1; v[2] = 2*x; for(n = 2, N, my(i = n + 1); v[i] = 2*x*v[i - 1] + (x - x^2)*v[i - 2]); v};
row(n, p) = {my(c = Vecrev(p)); c = concat(c, vector(n + 1 - #c)); c};
T(N) = {my(v = P(N)); concat(vector(#v, i, row(i - 1, v[i])))};
T(9)

polytool c48629374597

A202064 reversed triangle, offset 0, from P0
%e Example
Triangle begins:
  0:  1;
  1:  2,   0;
  2:  3,   1,   0;
  3:  4,   4,   0,   0;
  4:  5,  10,   1,   0,  0;
  5:  6,  20,   6,   0,  0, 0;
  6:  7,  35,  21,   1,  0, 0, 0;
  7:  8,  56,  56,   8,  0, 0, 0, 0;
  8:  9,  84, 126,  36,  1, 0, 0, 0, 0;
  9: 10, 120, 252, 120, 10, 0, 0, 0, 0, 0;
%F Formula
Row n lists the coefficients of P(n,x) in descending powers of x, where P(n,x) = 2*x*P(n-1,x) + (x-x^2)*P(n-2,x) for n >= 2, with P(0,x) = 1, P(1,x) = 2*x.
%t Mathematica
P[0, x_] := 1;
P[1, x_] := 2*x;
P[n_, x_] := P[n, x] = Expand[2*x*P[n - 1, x] + (x - x^2)*P[n - 2, x]];
Table[Reverse[PadRight[CoefficientList[P[n, x], x], n + 1]], {n, 0, 9}] // Flatten
%o PARI/GP
P(N) = {my(v = vector(N + 1)); v[1] = 1; v[2] = 2*x; for(n = 2, N, my(i = n + 1); v[i] = 2*x*v[i - 1] + (x - x^2)*v[i - 2]); v};
row(n, p) = {my(c = Vecrev(p)); c = concat(c, vector(n + 1 - #c)); c = Vecrev(c); c};
T(N) = {my(v = P(N)); concat(vector(#v, i, row(i - 1, v[i])))};
T(9)

polytool c48629374597

Properties

Proof chains ? JSON

  • Liu–Wang theorem for three-term recurrences [LW07, Thm 2.1, Thm 2.3, Cor 2.4, Prop 3.3] polytool ? step › direct check

Same fingerprint ?

References

  1. [LW07] Lily L. Liu and Yi Wang. A unified approach to polynomial sequences with only real zeros. Advances in Applied Mathematics, 38(4):542–560, May 2007. doi:10.1016/j.aam.2006.02.003