A124860 → x ↦ x/(x+1)

nonnegative coefficientsonly rational roots

Proved for all n all roots real, in [−1, 0]coefficients of one signHadamard kernel

Recurrence

\(\left(1 + 2\,x + x^{2}\right)\,P_{n}(x) = \left(2 + 12\,x + 26\,x^{2} + 24\,x^{3} + 8\,x^{4}\right)\,P_{n-2}(x) + \left(1 + 4\,x + 5\,x^{2} + 2\,x^{3}\right)\,P_{n-1}(x)\)
\(P_{0}(x) = 1\)
\(P_{1}(x) = 1 + 2\,x\)

Rows ?

nx0x1x2x3x4x5x6x7x8x9x10x11x12x13x14Pn(1)
011
1123
23121227
35306040135
41188264352176891
521210840168016806725103
64351625806880103208256275231347
785119071402380047600571203808010880185895
817127361915276608191520306432306432175104437761121931
93416138491042291526874561374912183321615713287856641745926711903
1068313660122940655680229488055077129179520104908807868160349696069939240330467
11136530030300300180180072072002018016040360320576576005765760038438400153753602795520241805655
122731655447209844806560216295206921446416150041627685785634607232030761984018457190467117056111861761451365371
135461141986170383212494768624738402249058245997488641199497728179924659219991628801599330304872361984290787328447365128706597903
1410923305844397597231807776174942768699771072209931321647984302088397252864111963371521119633715281427906564071395328125273702417896243252244370387
Technical details
Node id
n-4a6b9237eddcc625 · revision 0 · JSON
Definition source
derived:mobius_x_over_x_plus_one
Fingerprint
f6-11aec07ce60b6d61

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): yes

Matches ?

No OEIS matches.

Submission text ?

Atlas rows n = 0, …, ascending powers of x
%e Example
Triangle begins:
  0:   1;
  1:   1,    2;
  2:   3,   12,    12;
  3:   5,   30,    60,     40;
  4:  11,   88,   264,    352,    176;
  5:  21,  210,   840,   1680,   1680,     672;
  6:  43,  516,  2580,   6880,  10320,    8256,    2752;
  7:  85, 1190,  7140,  23800,  47600,   57120,   38080,   10880;
  8: 171, 2736, 19152,  76608, 191520,  306432,  306432,  175104,  43776;
  9: 341, 6138, 49104, 229152, 687456, 1374912, 1833216, 1571328, 785664, 174592;
%F Formula
The row polynomials satisfy (1+2*x+x^2)*P(n,x) = (2+12*x+26*x^2+24*x^3+8*x^4)*P(n-2,x) + (1+4*x+5*x^2+2*x^3)*P(n-1,x) for n >= 2, with P(0,x) = 1, P(1,x) = 1 + 2*x.
%t Mathematica
P[0, x_] := 1;
P[1, x_] := 1 + 2*x;
P[n_, x_] := P[n, x] = Expand[Together[((2 + 12*x + 26*x^2 + 24*x^3 + 8*x^4)*P[n - 2, x] + (1 + 4*x + 5*x^2 + 2*x^3)*P[n - 1, x])/(1 + 2*x + x^2)]];
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] = 1 + 2*x; for(n = 2, N, my(i = n + 1); v[i] = ((2 + 12*x + 26*x^2 + 24*x^3 + 8*x^4)*v[i - 2] + (1 + 4*x + 5*x^2 + 2*x^3)*v[i - 1])/(1 + 2*x + x^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

Properties

Proof chains ? JSON

Same fingerprint ?

References

  1. [Bra15] Petter Brändén. Unimodality, log-concavity, real-rootedness and beyond. Handbook of enumerative combinatorics, :437–483, March 2015. doi:10.1201/b18255-10
  2. [SP14] J Schur and G Polya. Über zwei Arten von Faktorenfolgen in der Theorie der algebraischen Gleichungen. J. Reine Angew. Math., 1914.