Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #4 Mar 31 2012 12:35:25
%S 1,4,9,25,48,113,189,367,598,1031,1559,2566,3681,5593,7926,11480,
%T 15598,21984,29080,39672,51688,68384,87284,113869,142723,181944,
%U 225921,283427,346610,430023,519663,635875,762786,921749,1094895,1313500,1545683
%N Number of nondecreasing integer sequences of length 9 with sum zero and sum of absolute values 2n.
%C a(n) = A000041(n)^2 for n<=4
%C a(n) = A000041(n)^2 - cumulative A000712(2*n-1-length), 0 <= 2*n-1-length <= floor(n/2) [empirical].
%H R. H. Hardin, <a href="/A158143/b158143.txt">Table of n, a(n) for n=1..643</a>
%K nonn
%O 1,2
%A _R. H. Hardin_ Mar 13 2009