A100862 → θ+1

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: 1;
  1: 1,  2;
  2: 1,  6,    3;
  3: 1, 12,   18,     4;
  4: 1, 20,   63,    40,     5;
  5: 1, 30,  165,   220,    75,     6;
  6: 1, 42,  360,   860,   600,   126,     7;
  7: 1, 56,  693,  2660,  3325,  1386,   196,    8;
  8: 1, 72, 1218,  6944, 14175, 10416,  2842,  288,   9;
  9: 1, 90, 1998, 15960, 49455, 59346, 27930, 5328, 405, 10;

The row polynomials satisfy -(2+(n^2+3*n-4)*x-(n^2+7*n)*x^2+2*n*x^3)*P(n,x) = -(2+(n^2+7*n-4)*x+(n^3+4*n^2-7*n-6)*x^2-(3*n^2+7*n+4)*x^3+(2*n+2)*x^4)*P(n-1,x) + (4*x^2+(2*n^2+10*n+4)*x^3-(4*n+4)*x^4)*d/dx P(n-1,x) for n >= 1, with P(0,x) = 1.

P[0, x_] := 1;
P[n_, x_] := P[n, x] = Expand[Together[(-(2 + (n^2 + 7*n - 4)*x + (n^3 + 4*n^2 - 7*n - 6)*x^2 - (3*n^2 + 7*n + 4)*x^3 + (2*n + 2)*x^4)*P[n - 1, x] + (4*x^2 + (2*n^2 + 10*n + 4)*x^3 - (4*n + 4)*x^4)*D[P[n - 1, x], x])/(-2 - (n^2 + 3*n - 4)*x + (n^2 + 7*n)*x^2 - 2*n*x^3)]];
Table[CoefficientList[P[n, x], x], {n, 0, 9}] // Flatten

P(N) = {my(v = vector(N + 1)); v[1] = 1; for(n = 1, N, my(i = n + 1); v[i] = (-(2 + (n^2 + 7*n - 4)*x + (n^3 + 4*n^2 - 7*n - 6)*x^2 - (3*n^2 + 7*n + 4)*x^3 + (2*n + 2)*x^4)*v[i - 1] + (4*x^2 + (2*n^2 + 10*n + 4)*x^3 - (4*n + 4)*x^4)*deriv(v[i - 1], x))/(-2 - (n^2 + 3*n - 4)*x + (n^2 + 7*n)*x^2 - 2*n*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)

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-54bc083045b2db5f
• 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-54bc083045b2db5f
• 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-54bc083045b2db5f
• 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-54bc083045b2db5f

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 euler_polynomial, shift 0 e-54bc083045b2db5f

  Laguerre’s theorem on multiplier sequences [SP14; Bra15, Thm 40] polytool ?

  • premise (sequence): Triangle read by rows: T(n,k) is the number of k-matchings of the corona K'(n) of the complete graph K(n) and the compl…
    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-e7942008ad3e1420 root: theorem check

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

    • preserver_image reversal, shift 0 e-7078061f6d32a158

      Affine, reversal and Möbius substitutions (elementary) polytool ?

      • premise (sequence): Triangle read by rows: T(n,k) is the number of k-matchings of the corona K'(n) of the complete graph K(n) and the compl…
        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-e7942008ad3e1420 (expanded above)

Related sequences ?

No candidate equalities or related sequences.

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