OFFSET
1,5
COMMENTS
For any power series f(x) starting with the term x the first column of the Kedlaya-Wilf matrix are the coefficients of f(x), the second column are the coefficients of f(f(x)), the third column are the coefficients of f(f(f(x))) and so on. This gives a matrix with first row consisting of ones. The sequence given is the diagonal reading of this matrix from right up to left down.
LINKS
Kiran S. Kedlaya, Another Combinatorial Determinant, Journal of Combinatorial Theory Series A 90(1), November 1998.
FORMULA
As an n X n matrix a(i,j) = coefficient of x^i in f^(j)(x) for i,j=1..n where f^(j) is the j-fold composition of f with itself.
EXAMPLE
f^(3)(x) = x + 3x^2 + 12x^4 + ... as in A283679, so a(4)=1, a(8)=3, a(13)=12.
MAPLE
h:= x-> x/(1-x-x^2):
h2:= n-> coeff(series(h(h(x))), x, n+1), x, n):
h3:= n -> coeff(series(h(h2(x))), x, n+1), x, n):
etc.
h7:= n -> coeff(series(h(h6(x))), x, n+1), x, n): N7:=array(1..7, 1..7, sparse): gg:=array([h1, h2, h3, h4, h5, h6, h7]):for k from 1 to 7 do: for j from 1 to 7 do: N7[k, j]:=coeff(series(gg[j], x, 12), x^k): od:od:
CROSSREFS
KEYWORD
AUTHOR
Oboifeng Dira, Apr 30 2017
STATUS
approved