OFFSET
0,3
COMMENTS
The condition that the rows be in decreasing order is equivalent to considering nonequivalent matrices with distinct rows up to permutation of rows.
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..400
PROG
(PARI) a(n)={my(p=prod(i=0, n, prod(j=0, n, 1 + x^i*y^j + O(x*x^n) + O(y*y^n))), q=prod(i=1, n, 1 + x^i + O(x*x^n))); polcoef(polcoef(p, n), n)/2 - polcoef(q, n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Jan 13 2020
STATUS
approved