Real-rooted atlas

A106246 → basis A007318 → x ↦ x/(x+1)

nonnegative coefficients

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

Recurrence

\(\left(1 + 3\,x + 3\,x^{2} + x^{3}\right)\,P_{n}(x) = \left(1 + 9\,x + 33\,x^{2} + 63\,x^{3} + 66\,x^{4} + 36\,x^{5} + 8\,x^{6}\right)\,P_{n-3}(x) + \left(-3 - 21\,x - 57\,x^{2} - 75\,x^{3} - 48\,x^{4} - 12\,x^{5}\right)\,P_{n-2}(x) + \left(3 + 15\,x + 27\,x^{2} + 21\,x^{3} + 6\,x^{4}\right)\,P_{n-1}(x)\)
\(P_{0}(x) = 1\)
\(P_{1}(x) = 3 + 4\,x\)
\(P_{2}(x) = 6 + 18\,x + 13\,x^{2}\)

Rows ?

nx0x1x2x3x4x5x6x7Pn(1)
011
1347
26181337
310487538171
415100246264104729
52118061010208402722943
628294127529203720249668811421
7364482373693012040124327056169643011

All 15 rows

Technical details
Node id
n-c8d373cfb3ed639a · revision 0 · JSON
Definition source
derived:mobius_x_over_x_plus_one
Fingerprint
f6-5fde68fef36ef0af

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 ?

No OEIS matches.

Submission text ?

Atlas rows n = 0, …, ascending powers of x
%e Example
Triangle begins:
  0:  1;
  1:  3,   4;
  2:  6,  18,   13;
  3: 10,  48,   75,    38;
  4: 15, 100,  246,   264,   104;
  5: 21, 180,  610,  1020,   840,    272;
  6: 28, 294, 1275,  2920,  3720,   2496,    688;
  7: 36, 448, 2373,  6930, 12040,  12432,   7056,   1696;
  8: 45, 648, 4060, 14448, 31920,  44800,  38976,  19200,  4096;
  9: 55, 900, 6516, 27384, 73584, 131040, 154560, 116352, 50688, 9728;
%F Formula
The row polynomials satisfy (1+3*x+3*x^2+x^3)*P(n,x) = (1+9*x+33*x^2+63*x^3+66*x^4+36*x^5+8*x^6)*P(n-3,x) - (3+21*x+57*x^2+75*x^3+48*x^4+12*x^5)*P(n-2,x) + (3+15*x+27*x^2+21*x^3+6*x^4)*P(n-1,x) for n >= 3, with P(0,x) = 1, P(1,x) = 3 + 4*x, P(2,x) = 6 + 18*x + 13*x^2.
%t Mathematica
P[0, x_] := 1;
P[1, x_] := 3 + 4*x;
P[2, x_] := 6 + 18*x + 13*x^2;
P[n_, x_] := P[n, x] = Expand[Together[((1 + 9*x + 33*x^2 + 63*x^3 + 66*x^4 + 36*x^5 + 8*x^6)*P[n - 3, x] - (3 + 21*x + 57*x^2 + 75*x^3 + 48*x^4 + 12*x^5)*P[n - 2, x] + (3 + 15*x + 27*x^2 + 21*x^3 + 6*x^4)*P[n - 1, x])/(1 + 3*x + 3*x^2 + x^3)]];
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] = 3 + 4*x; v[3] = 6 + 18*x + 13*x^2; for(n = 3, N, my(i = n + 1); v[i] = ((1 + 9*x + 33*x^2 + 63*x^3 + 66*x^4 + 36*x^5 + 8*x^6)*v[i - 3] - (3 + 21*x + 57*x^2 + 75*x^3 + 48*x^4 + 12*x^5)*v[i - 2] + (3 + 15*x + 27*x^2 + 21*x^3 + 6*x^4)*v[i - 1])/(1 + 3*x + 3*x^2 + x^3)); 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

References

  1. [ASW52] Michael Aissen, I. J. Schoenberg and A. M. Whitney. On the generating functions of totally positive sequences I. Journal d’Analyse Mathématique, 2(1):93–103, 1952. doi:10.1007/BF02786970
  2. [AW24] Christos A. Athanasiadis and David G. Wagner. Veronese sections and interlacing matrices of polynomials and formal power series. arXiv:2404.12989. arXiv
  3. [Bra06] Petter Brändén. On linear transformations preserving the Pólya frequency property. Transactions of the American Mathematical Society, 358(8):3697–3716, February 2006. doi:10.1090/s0002-9947-06-03856-6
  4. [Bra15] Petter Brändén. Unimodality, log-concavity, real-rootedness and beyond. Handbook of enumerative combinatorics, :437–483, March 2015. doi:10.1201/b18255-10
  5. [Edr53] Albert Edrei. Proof of a Conjecture of Schoenberg on the Generating Function of a Totally Positive Sequence. Canadian Journal of Mathematics, 5:86–94, 1953. doi:10.4153/CJM-1953-010-3
  6. [SP14] J Schur and G Polya. Über zwei Arten von Faktorenfolgen in der Theorie der algebraischen Gleichungen. J. Reine Angew. Math., 1914.