A185263 Triangle T(n,k) read by rows: coefficients (in compressed forms) in order of decreasing exponents of polynomials p_n(t) related to Hultman numbers.

1, 1, 1, 1, 1, 5, 1, 15, 8, 1, 35, 84, 1, 70, 469, 180, 1, 126, 1869, 3044, 1, 210, 5985, 26060, 8064, 1, 330, 16401, 152900, 193248, 1, 495, 39963, 696905, 2286636, 604800, 1, 715, 88803, 2641925, 18128396, 19056960, 1, 1001, 183183, 8691683, 109425316, 292271616, 68428800, 1, 1365, 355355, 25537655, 539651112, 2961802480, 2699672832

Offset

0,6

Comments

Row n contains floor(n/2) + 1 terms.

Links

Gheorghe Coserea, Rows n = 0..202, flattened

Nikita Alexeev and Peter Zograf, Hultman numbers, polygon gluings and matrix integrals, arXiv preprint arXiv:1111.3061 [math.PR], 2011.

Formula

From Gheorghe Coserea, Jan 29 2018: (Start)

p(n) = Sum_{k=0..floor(n/2)} T(n,k)*t^(n+1-2*k) satisfies (n+2)*p(n) = (2*n+1)*t*p(n-1) + (n-1)*(n^2-t^2)*p(n-2), n >= 2. (th. 3, (iii))

E.g.f. A(x;t) = Sum_{n>=0} p(n)*x^n/n! = ((1-x)^(-t) - (1+x)^t)/x^2. (th. 3, (i))

T(n,k) = -Stirling1(n+2, n+1-2*k)/binomial(n+2,2), where Stirling1(n,k) is defined by A048994.

A000142(n) = p(n)(1), A052572(n) = p(n)(2) for n > 0, A060593(n) = T(2*n, n) for n > 0. (End)

n-th row polynomial R(n,x) satisfies x*R(n,x^2) = (1/2)*( P(n+1,x) - P(n+1,-x) )/ binomial(n+2,2), where P(k,x) = (1 + x)*(1 + 2*x) * ... *(1 + k*x). - Peter Bala, May 14 2023

Example

Triangle begins:
  n\k| 0    1      2       3         4         5        6
-----+---------------------------------------------------
   0 | 1
   1 | 1
   2 | 1    1
   3 | 1    5
   4 | 1   15      8
   5 | 1   35     84
   6 | 1   70    469     180
   7 | 1  126   1869    3044
   8 | 1  210   5985   26060      8064
   9 | 1  330  16401  152900    193248
  10 | 1  495  39963  696905   2286636    604800
  11 | 1  715  88803 2641925  18128396  19056960
  12 | 1 1001 183183 8691683 109425316 292271616 68428800
  ...
Polynomials p_n(t):
  p_0 = t;
  p_1 = t^2;
  p_2 = t^3 +     t;
  p_3 = t^4 +   5*t^2;
  p_4 = t^5 +  15*t^3 +    8*t;
  p_5 = t^6 +  35*t^4 +   84*t^2;
  p_6 = t^7 +  70*t^5 +  469*t^3 +  180*t;
  p_7 = t^8 + 126*t^6 + 1869*t^4 + 3044*t^2;
  ...
A(x;t) = t + t^2*x/1! + (t^3 + t)*x^2/2! + (t^4 + 5*t^2)*x^3/3! + ...

Mathematica

T[n_, k_] := Abs[StirlingS1[n+2, n-2k+1]]/Binomial[n+2, 2];
Table[T[n, k], {n, 0, 13}, {k, 0, n/2}] // Flatten (* Jean-François Alcover, Aug 12 2018 *)

Prog

(PARI)
seq(N) = {
  my(p=vector(N), t='t, v); p[1] = t^2; p[2] = t^3 + t;
  for (n=3, N,
    p[n] = ((2*n+1)*t*p[n-1] + (n-1)*(n^2-t^2)*p[n-2])/(n+2));
  v = vector(#p, n, vector(1+n\2, k, polcoeff(p[n], n+1-2*(k-1))));
  concat([[1]], v);
};
concat(seq(13))
(PARI)
N=14; x='x+O('x^(N+1));
concat(apply(p->select(a->a!=0, Vec(p)), Vec(serlaplace(((1-x)^(-t) - (1+x)^t)/x^2))))
(PARI)
T(n, k) = -stirling(n+2, n+1-2*k, 1)/binomial(n+2, 2);
concat(1, concat(vector(13, n, vector(1+n\2, k, T(n, k-1)))))
\\ Gheorghe Coserea, Jan 29 2018

Crossrefs

Cf. A038720, A048994, A060593, A185259.

For uncompressed form of polynomial coefficients, in order of increasing powers, see A164652.

Sequence in context: A087727 A039807 A213590 * A264616 A157395 A157385

Adjacent sequences: A185260 A185261 A185262 * A185264 A185265 A185266

Keyword

nonn,tabf

Author

N. J. A. Sloane, Jan 21 2012

Extensions

More terms from Gheorghe Coserea, Jan 29 2018

Status

approved