A219570: Triangular array read by rows. T(n,k) is the number of necklaces (turning over is not allowed) of n labeled black or white beads having exactly k black beads.

Matches ?

Row sums ? A066318, A032184

Submission text ?

Triangle begins:
  0:     0;
  1:     1,      1;
  2:     1,      2,       1;
  3:     2,      6,       6,       2;
  4:     6,     24,      36,      24,       6;
  5:    24,    120,     240,     240,     120,      24;
  6:   120,    720,    1800,    2400,    1800,     720,     120;
  7:   720,   5040,   15120,   25200,   25200,   15120,    5040,     720;
  8:  5040,  40320,  141120,  282240,  352800,  282240,  141120,   40320,   5040;
  9: 40320, 362880, 1451520, 3386880, 5080320, 5080320, 3386880, 1451520, 362880, 40320;

The row polynomials satisfy (n-1)*P(n,x) = (n^2-2*n+1+(n^2-2*n+1)*x)*P(n-1,x) for n >= 2, with P(0,x) = 0, P(1,x) = 1 + x.

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

P(N) = {my(v = vector(N + 1)); v[1] = 0; v[2] = 1 + x; for(n = 2, N, my(i = n + 1); v[i] = ((n^2 - 2*n + 1 + (n^2 - 2*n + 1)*x)*v[i - 1])/(n - 1)); 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)

Properties

• Real-rooted? Every row P_n, n ≥ 1, is zero or real-rooted with all roots in (−∞, 0]
  by Iterated real-rootedness preservers
• Coefficients of one sign? Every nonzero row, n ≥ 1: the coefficients of P_n have one sign
  derived from Iterated real-rootedness preservers
• Hadamard kernel (Malo)? Rows P_n, n ≥ 1, are Hadamard kernels (preserve real-rootedness)
  derived from Iterated real-rootedness preservers
• Interlacing of consecutive rows? Rows P_(m-1), P_m interlace (weak, previous interlaces next) for every m ≥ 2
  by Iterated real-rootedness preservers

Proof chains ? JSON

• Iterated real-rootedness preservers [SP14; Bra15, Thm 7.1 of arXiv:1410.6601; Bra06, Cor 3.5] polytool ? step › direct check

Related ?

Same fingerprint ?

• Triangle whose (i,j)-th entry is binomial(i,j)*12^(i-j)*12^j.
• A178822: Triangle read by rows: T(n,k) = C(n+5,5) * C(n,k), 0 <= k <= n.
• A027465 → basis A013611
• basis-map coefficients of A026729, shifted → basis A007318
• basis-map coefficients of Triangle read by rows: row n consists of n-1 zeros followed by Fibonacci(n).
• A028326 → basis A013609
• A038208: Triangle whose (i,j)-th entry is binomial(i,j)*2^i.
• A376827: T(n, k) = binomial(n, k)*hypergeom([(1 - n)/2, -n/2], [1], 4).
• veronese parent of Triangle T(n,k) with diagonals T(n,n-k) = binomial(n,3k).
• basis-map coefficients of A113214, shifted → D
• A094305: Triangle read by rows: T(n,k) = ((n+1)(n+2)/2) * binomial(n,k) (0 <= k <= n).
• A038338 → basis A013609
• A216973 → D
• A258758: Triangle T(n,k) = C(n+k-1,k)*C(2*n-1,n-k).
• A134058: Triangle T(n, k) = 2*binomial(n, k) with T(0, 0) = 1, read by rows.
• A120910 → basis A013610
• A178821: Triangle read by rows: T(n,k) = binomial(n+4,4) * binomial(n,k), 0 <= k <= n.
• Riordan array (1-x,x/(1-x)).
• A134346: Triangle read by rows: T(n,k) = (2^(n+1)-1)*binomial(n,k).
• A216973: Exponential Riordan array [x*exp(x),x].
• A085880 → basis A013609
• A178820: Triangle read by rows: T(n,k) = C(n+3,3) * C(n,k), 0 <= k <= n.
• A356546: Triangle read by rows. T(n, k) = RisingFactorial(n + 1, n) / (k! * (n - k)!).
• A038325 → basis A013609
• A085880 → D
• A344565: Triangle read by rows, for 0 <= k <= n: T(n, k) = binomial(n, k) * binomial(binomial(n + 3, 2), 2).
• A135838: Triangle read by rows: T(n,k) = 2^floor(n/2)*binomial(n-1,k-1).
• A156992 → basis A013609
• A085881 → basis A013609
• A135065 → D
• A178821 → basis A013609
• basis-map coefficients of A026729 → basis A007318
• A094305 → D
• A156992: Triangle T(n,k) = n!*binomial(n-1, k-1) for 1 <= k <= n, read by rows.
• A127952: Triangle read by rows, T(n,k) = (n+1)*binomial(n-1,k-1).
• A178822 → D
• A134059: Triangle T(n, k) = 3*binomial(n,k) with T(0, 0) = 1, read by rows.
• A356546 → basis A013609
• A028326: Twice Pascal's triangle A007318: T(n,k) = 2*C(n,k).
• A178820 → D
• basis-map coefficients of A021012 → x ↦ x+1
• A085881: Triangle T(n,k) read by rows: multiply row n of Pascal's triangle (A007318) by A001147(n).
• A038330 → basis A013611
• veronese parent of Binomial coefficients C(n,k) with n-k odd, read by rows.
• A178820 → basis A013609
• A129533: Array read by antidiagonals: T(n,k) = binomial(n+1,2)*binomial(n+k,n+1) for 0 <= k <= n.
• A132200: Numbers in (4,4)-Pascal triangle .
• A124860: A Jacobsthal-Pascal triangle.
• veronese parent of Triangle T(n,k) with diagonals T(n,n-k) = binomial(n,3k).
• veronese parent of Triangle T(n,k) with diagonals T(n,n-k) = binomial(n,3k).
• A038208 → D
• A135838 → D
• basis-map coefficients of A113214, shifted → basis A013609
• A097805: Number of compositions of n with k parts, T(n, k) = binomial(n-1, k-1) for n, k >= 1 and T(n, 0) = 0^n, triang…
• Second weight array of Pascal's triangle (formatted as a rectangle), by antidiagonals.
• A038325: Triangle read by rows whose (i,j)-th entry is binomial(i,j)*11^(i-j)*11^j.
• basis-map coefficients of A112227 → x ↦ x+1
• A380114: Triangle read by rows: The convolution triangle of 2^n, where the convolution triangle of a sequence is define…
• basis-map coefficients of Riordan array (1+2x,x(1+x)). shifted by x -> -x + 0
• A344565 → basis A013609
• A196347: Triangle T(n, k) read by rows, T(n, k) = n!*binomial(n, k).
• A135065: A127733 * A007318 as infinite lower triangular matrices.
• A038221: Triangle whose (i,j)-th entry is binomial(i,j)*3^(i-j)*3^j.
• A178822 → basis A013609
• A196347 → basis A013609
• A028326 → D
• A038221 → basis A013609
• A135838 → basis A013609
• A003506: Triangle of denominators in Leibniz's Harmonic Triangle a(n,k), n >= 1, 1 <= k <= n.
• A007318: Binomial
• A135089: Triangle T(n,k) = 5*binomial(n,k) with T(0,0) = 1, read by rows.
• A131431 → x ↦ x+1
• A344565 → D
• A007318 → ×(−(1/2)n+(1/2)n²) → D
• A237765: Triangular array read by rows: T(n,k) = binomial(n,2)*binomial(n,k), n>=0, 0<=k<=n.
• veronese parent of Binomial coefficients C(n,k) with n-k even, read by rows.
• A178821 → D
• A085880: Triangle T(n,k) read by rows: multiply row n of Pascal's triangle (A007318) by the n-th Catalan number (A00010…

References

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