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A134991 Triangle of Ward numbers T(n,k) read by rows. 18
1, 1, 3, 1, 10, 15, 1, 25, 105, 105, 1, 56, 490, 1260, 945, 1, 119, 1918, 9450, 17325, 10395, 1, 246, 6825, 56980, 190575, 270270, 135135, 1, 501, 22935, 302995, 1636635, 4099095, 4729725, 2027025, 1, 1012, 74316, 1487200, 12122110, 47507460 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

This is a reordered version of A008299 read along the diagonals (see table on p. 222 in Comtet) and a row-reversed version of a table on p. 92 in the Ward reference (and A181996, with an additional leading 1). A134685 is a refinement of the Ward table. The first and second diagonals are A001147 and A000457 and appear in the diagonals of several OEIS entries. The polynomials also appear in Carlitz (p. 85), Drake et al. (p. 8) and Smiley (p. 7).

First few polynomials (with a different offset) are

P(0,t) = 0

P(1,t) = 1

P(2,t) = t

P(3,t) = t + 3 t^2

P(4,t) = t + 10 t^2 + 15 t^3

P(5,t) = t + 25 t^2 + 105 t^3 + 105 t^4

These are the "face" numbers of the tropical Grassmannian G(2,n),related to phylogenetic trees (with offset 0 beginning with P(2,t)). Corresponding h-vectors are A008517. - Tom Copeland, Oct 03 2011

A133314 applied to the derivative of A(x,t) implies (a.+b.)^n = 0^n , for (b_n)=P(n+1,t) and (a_0)=1, (a_1)=-t, and (a_n)=-(1+t) P(n,t) otherwise. E.g., umbrally, (a.+b.)^2 = a_2*b_0 + 2 a_1*b_1 + a_0*b_2 =0. - Tom Copeland, Oct 08 2011

REFERENCES

L. Carlitz, The coefficients in an asymptotic expansion and certain related numbers, Duke Math. J., vol 35 (1968), p. 83-90.

Clark, Lane, Asymptotic normality of the Ward numbers. Discrete Math. 203 (1999), no. 1-3, 41-48. [From N. J. A. Sloane, Feb 06 2012]

L. Comtet, Advanced Combinatorics, Reidel, 1974.

B. Drake, I. M. Gessel and G. Xin, Three proofs and a generalization of the Goulden-Litsyn-Shevelev conjecture ..., J. Integer Sequences, Vol. 10 (2007), #07.3.7.

M. Ward, The representations of Stirling's numbers and Stirling's polynomials as sums of factorials, Amer. J. Math., 56 (1934), p. 87-95.

LINKS

Table of n, a(n) for n=1..42.

J. Fernando Barbero G., Jesús Salas, Eduardo J. S. Villaseñor, Bivariate Generating Functions for a Class of Linear Recurrences. I. General Structure, arXiv:1307.2010, 2013

J. F. Barbero G., J. Salas and E. J. S. Villaseñor, Bivariate Generating Functions for a Class of Linear Recurrences. II. Applications, arXiv preprint arXiv:1307.5624, 2013

A. Blass, N. Dobrinen, D. Raghavan, The next best thing to a P-point, arXiv preprint arXiv:1308.3790, 2013

MathOverflow, Face numbers for tropical Grassmannian G'_2,7 simplicial complex?

L. M. Smiley, Completion of a Rational Function Sequence of Carlitz

FORMULA

E.g.f. for the polynomials is A(x,t) = (x-t)/(t+1) + T{ (t/(t+1)) * exp[(x-t)/(t+1)] }, where T(x) is the Tree function, the e.g.f. of A000169. The compositional inverse in x (about x = 0) is B(x) = x + -t * [exp(x) - x - 1]. Special case t = 1 gives e.g.f. for A000311. These results are a special case of A134685 with u(x) = B(x).

Contribution from Tom Copeland, Oct 26 2008: (Start)

Umbral-Sheffer formalism gives, for m a positive integer and u = t/(t+1),

[P(.,t)+Q(.,x)]^m = [m Q(m-1,x) - t Q(m,x)]/(t+1) + sum(n>=1) { n^(n-1)[u exp(-u)]^n/n! [n/(t+1)+Q(.,x)]^m }, when the series is convergent for a sequence of functions Q(n,x).

Check: With t=1; Q(n,x)=0^n, for n>=0; and Q(-1,x)=0, then [P(.,1)+Q(.,x)]^m = P(m,1) = A000311(m).

(End)

Let h(x,t) = 1/(dB(x)/dx) = 1/(1-t*(exp(x)-1)), an e.g.f. in x for row polynomials in t of A019538, then the n-th row polynomial in t of the table A134991, P(n,t), is given by ((h(x,t)*d/dx)^n)x evaluated at x=0, i.e., A(x,t) = exp(x*P(.,t)) = exp(x*h(u,t)*d/du) u evaluated at u=0. Also, dA(x,t)/dx = h(A(x,t),t). - Tom Copeland, Sep 05 2011

The polynomials (1+t)/t*P(n,t) are the row polynomials of A112493. Let f(x) = (1+x)/(1-x*t). Then for n >= 0, P(n+1,t) is given by t/(1+t)*(f(x)*d/dx)^n(f(x)) evaluated at x = 0. - Peter Bala, Sep 30 2011

Contributions from Tom Copeland, Oct 04 2011: (Start)

a(n,k)=(k+1)a(n-1,k)+(n+k+1)a(n-1,k-1) with starting indices n=0 and k=0 beginning with P(2,t) (as suggested by a formula of David Speyer on MathOverflow). a(n,k)= k a(n-1,k)+(n+k-1)a(n-1,k-1) with starting indices n=1 and k=1 of table (cf. Smiley above and Riordin ref.[10] therein).

P(n,t) = (1/(1+t))^n sum(k=1 to infin) k^(n+k-1) [(u*exp(-u)]^k / k! with u=(t/(t+1)) for n>1; therefore, sum(k=1 to infin) (-1)^k k^(n+k-1) x^k/k!

  = [1+LW(x)]^(-n) P{n,-LW(x)/[1+LW(x)]}, with LW(x) the Lambert W-Fct.

a(n,k)= sum(i=0 to k) {(-1)^i binom(n+k,i) sum(j=0 to k-i) (-1)^j (k-i-j)^(n+k-i)/[j!(k-i-j)!]} from relation to A008299. (End)

The e.g.f. A(x,t) = -v * { sum(j=1 to infin) D(j-1,u) (-z)^j / j! } where u=(x-t)/(1+t) , v=1+u, z= x/[(1+t) v^2] and D(j-1,u) are the polynomials of A042977. dA/dx= 1/[(1+t)(v-A)]= 1/{1-t*[exp(A)-1]}.- Tom Copeland, Oct 06 2011

CROSSREFS

Cf. A112493. A181996 is the mirror image.

Sequence in context: A068438 A064060 A176740 * A212930 A225725 A095327

Adjacent sequences:  A134988 A134989 A134990 * A134992 A134993 A134994

KEYWORD

nonn,tabl

AUTHOR

Tom Copeland, Feb 05 2008

EXTENSIONS

Edited by N. J. A. Sloane, Apr 05 2012

STATUS

approved

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Last modified April 16 10:15 EDT 2014. Contains 240577 sequences.