A081581 → D

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.

Triangle begins:
  0:  0;
  1:  1;
  2:  8,    2;
  3: 15,   30,     3;
  4: 22,  156,    66,      4;
  5: 29,  380,   570,    116,      5;
  6: 36,  702,  2544,   1404,    180,     6;
  7: 43, 1122,  7017,   9356,   2805,   258,    7;
  8: 50, 1640, 15018,  39064,  25030,  4920,  350,   8;
  9: 57, 2256, 27576, 115224, 144030, 55152, 7896, 456, 9;

The row polynomials satisfy -(7*n^2-20*n+13-(7*n^2-5*n-2)*x+(n-1)*x^2)*P(n,x) = -(7*n^2-13*n+6+(91*n^2-359*n+228)*x-(34*n-44)*x^2+2*x^3)*P(n-1,x) + ((7*n-6)*x+(182*n-157)*x^2+(7*n-32)*x^3-x^4)*d/dx P(n-1,x) for n >= 2, with P(0,x) = 0, P(1,x) = 1.

P[0, x_] := 0;
P[1, x_] := 1;
P[n_, x_] := P[n, x] = Expand[Together[(-(7*n^2 - 13*n + 6 + (91*n^2 - 359*n + 228)*x - (34*n - 44)*x^2 + 2*x^3)*P[n - 1, x] + ((7*n - 6)*x + (182*n - 157)*x^2 + (7*n - 32)*x^3 - x^4)*D[P[n - 1, x], x])/(-7*n^2 + 20*n - 13 + (7*n^2 - 5*n - 2)*x - (n - 1)*x^2)]];
Table[CoefficientList[P[n, x], x], {n, 0, 9}] // Flatten

P(N) = {my(v = vector(N + 1)); v[1] = 0; v[2] = 1; for(n = 2, N, my(i = n + 1); v[i] = (-(7*n^2 - 13*n + 6 + (91*n^2 - 359*n + 228)*x - (34*n - 44)*x^2 + 2*x^3)*v[i - 1] + ((7*n - 6)*x + (182*n - 157)*x^2 + (7*n - 32)*x^3 - x^4)*deriv(v[i - 1], x))/(-7*n^2 + 20*n - 13 + (7*n^2 - 5*n - 2)*x - (n - 1)*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)

Proved properties

• Real-rooted. Every row P_n, n >= 0, 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-9b4a6f1e706c7c02
• Coefficients of one sign. Every nonzero row, n >= 0: 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-9b4a6f1e706c7c02
• Hadamard kernel (Malo). Rows P_n, n >= 0, 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-9b4a6f1e706c7c02
• 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-9b4a6f1e706c7c02

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 derivative_polynomial, shift 0 e-9b4a6f1e706c7c02

  Laguerre’s theorem on differential operators [SP14] polytool ?

  • premise (sequence): Pascal-(1,6,1) array.
    uses: Every row P_n, n >= 0, is zero or real-rooted with all roots in (-inf, 0]
    • theorem_check liu_wang_derivative_lag e-dfce858c9d52dee3 root: theorem check

      Liu–Wang theorem with a lag row [LW07, Thm 2.1] RealRooted ?

    • preserver_image reversal, shift 0 e-5c5351a0cb2ba1df

      Affine, reversal and Möbius substitutions (elementary) polytool ?

      • premise (sequence): Pascal-(1,6,1) array.
        uses: Every row P_n, n >= 0, is zero or real-rooted with all roots in (-inf, 0]
        • ↵ theorem_check liu_wang_derivative_lag e-dfce858c9d52dee3 (expanded above)

Related sequences ?

No candidate equalities or related sequences.

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
2. [SP14] J Schur and G Polya. Über zwei Arten von Faktorenfolgen in der Theorie der algebraischen Gleichungen. J. Reine Angew. Math., 1914.