OFFSET
1,5
FORMULA
G.f.: 1/(1-y*(x*(1+x)*(1-sqrt(1-4*x^2))/(2*x^2)))-1.
EXAMPLE
1;
1, 1;
1, 2, 1;
1, 3, 3, 1;
2, 4, 6, 4, 1;
2, 7, 10, 10, 5, 1;
5, 10, 18, 20, 15, 6, 1;
MAPLE
# Seen as a (0, 0)-based triangle:
gf := (2*(x + 1))/(sqrt(1 - 4*x^2) - 2*x*(x + 1)*y + 1):
serx := series(gf, x, 20): sery := n -> series(coeff(serx, x, n), y, 20):
row := n -> seq(coeff(sery(n), y, j), j=0..n):
seq(lprint(row(n)), n=0..9); # Peter Luschny, Feb 14 2019
PROG
(Maxima)
T(n, k):=k*sum((binomial(k, 2*k+2*i-n)*binomial(k+2*i-1, i))/(k+i), i, 0, (n-k)/2);
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Vladimir Kruchinin, Feb 13 2019
STATUS
approved