OFFSET
1,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..150
FORMULA
a(n) = [x^(n-1)] z/((n*x-1)*((n-1)*x-1)), where z = (n/2*x) if n is even, and z = (1-(n-1)/2*x) else.
EXAMPLE
a(3) = 14, because there are 14 ordered 3-tuples of positive integers such that the largest value is 3 and the first value is odd: 113, 123, 131, 132, 133, 311, 312, 313, 321, 322, 323, 331, 332, 333.
MAPLE
a:= n-> (Matrix (`if` (irem(n, 2)=0, [n/2, 0], [1 +(n-1)/2*3, 1])). Matrix ([[2*n-1, 1], [n*(1-n), 0]]) ^(n-1))[1, 2]: seq (a(n), n=1..20);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Nov 07 2009
STATUS
approved