%I #13 Oct 21 2019 16:24:01

%S 1,1,2,4,19,4,28,222,147,8,280,3194,4128,887,16,3640,55024,113566,

%T 52538,4835,32,58240,1107336,3268788,2562676,555684,25167,64,1106560,

%U 25526192,100544412,117517960,45415640,5301150,128203,128,24344320,663605680,3325767376,5352311764,3189383200,695714590,47537320,646519,256,608608000,19213911360,118361719296,248493947496,208996478388,72479948400,9696965250,410038434,3245139,512

%N Triangle T(n, k) read by rows: row n gives the coefficients of the numerator polynomials of the o.g.f. of the (n+1)-th diagonal of the Sheffer triangle A286718 (|S1hat[3,1]| generalized Stirling 1), for n >= 0.

%C The ordinary generating function (o.g.f.) of the (n+1)-th diagonal sequence of the Sheffer triangle A286718 = ((1 - 3*x)^(-1/3), -log(1 - 3*x)/3), called |S1hat[3,1]|, is GD(3,1;n,x) = P(n, x)/(1 - x)^(2*n+1), with the row polynomials P(n, x) = Sum_{k=0..n} T(n, k)*x^k, n >= 0.

%C For the two parameter Sheffer case |S1hat[d,a]| = ((1 - d*x)^{-a/d}, -log(1 - d*x)/d) (with gcd(d,a) = 1, d >=0, a >= 0, and for d = 1 one takes a = 0) the e.g.f. ED(t, x) of the o.g.f.s {GD(d,a;n,x)}_{n>=0} of the diagonal sequences with elements D(d,a;n,m) = |S1hat[d,a]|(n+m, m) (n=0 for the main diagonal) is of interest. It can be computed via Lagrange's theorem. For the special Sheffer case (1, f(x)) this has been done by P. Bala (see the link). This method can be generalized for Sheffer (g(x), f(x)), as shown in the W. Lang link.

%H Peter Bala, <a href="/A112007/a112007_Bala.txt">Diagonals of triangles with generating function exp(t*F(x)).</a>

%H Wolfdieter Lang, <a href="http://arxiv.org/abs/1708.01421">On Generating functions of Diagonal Sequences of Sheffer and Riordan Number Triangles</a>, arXiv:1708.01421 [math.NT], August 2017.

%F T(n, k) = [x^k] P(n, x) with the numerator polynomials of the o.g.f. GD(n, x) = P(n, x)/(1-x)^(2*n+1) of the (n+1)-th diagonal sequence of the triangle A286718. See a comment above.

%e The triangle T(n, k) begins:

%e n\k 0 1 2 3 4 5 6 7 ...

%e 0: 1

%e 1: 1 2

%e 2: 4 19 4

%e 3: 28 222 147 8

%e 4: 280 3194 4128 887 16

%e 5: 3640 55024 113566 52538 4835 32

%e 6: 58240 1107336 3268788 2562676 555684 25167 6

%e 7: 1106560 25526192 100544412 117517960 45415640 5301150 128203 128

%e ...

%e n = 8: 24344320 663605680 3325767376 5352311764 3189383200 695714590 47537320 646519 256,

%e n = 9: 608608000 19213911360 118361719296 248493947496 208996478388 72479948400 9696965250 410038434 3245139 512.

%e n = 3: The o.g.f. of the 4th diagonal sequence of A286718, [28, 418, 2485, ...] = A024213(n+1), n >= 0, is P(3, x) = (28 + 222*x + 147*x^2 + 8*x^3)/(1 - 3*x)^7.

%Y Cf. A024213, A286718, A288875 ([2,1] case).

%K nonn,tabl

%O 0,3

%A _Wolfdieter Lang_, Aug 08 2017