OFFSET
1,2
REFERENCES
P. A. MacMahon, Chess tournaments and the like treated by the calculus of symmetric functions, Coll. Papers I, MIT Press, 344-375.
LINKS
Qihao Ye, Table of n, a(n) for n = 1..1032
C. Bebeacua, T. Mansour, A. Postnikov and S. Severini, On the X-rays of permutations, arXiv:math/0506334 [math.CO], 2005.
FORMULA
Nonnegative integer points (p_1, p_2, ..., p_n) in polytope p_0=p_{n+1}=0, 2p_i -(p_{i+1}+p_{i-1}) <= 3, p_i >= 0, i=1, ..., n.
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved