OFFSET
0,3
COMMENTS
The case n=1 is exceptional and a(1) could be 0 or 1.
a(n) is the number of vertices of the uniform (n-4)_21 polytope. - Andrey Zabolotskiy, Oct 29 2018
REFERENCES
Yu. I. Manin, Rational surfaces and Galois cohomology, pp. 495-509 of Proc. International Congress Mathematicians, Moscow 1966.
Yu. I. Manin, Cubic Forms, Second edition, North-Holland Publishing Co., Amsterdam, 1986, page 136, Theorem 26.2(iii), Table (IV.9).
LINKS
M. Nagata, On rational surfaces, I, Mem. Coll. Sci. Univ. Kyoto, Ser. A., XXXII (No. 3, 1960).
M. Nagata, On rational surfaces, II, Mem. Coll. Sci. Univ. Kyoto, Ser. A., XXXIII (No. 2, 1960).
A. Neumaier, Lattices of simplex type, SIAM J. Algebraic Discrete Methods 4 (1983), no. 2, 145--160. The sequence is on page 153.
Wikipedia, Uniform k_21 polytope
EXAMPLE
G.f. = x + 3*x^2 + 6*x^3 + 10*x^4 + 16*x^5 + 27*x^6 + 56*x^7 + 240*x^8.
CROSSREFS
KEYWORD
fini,full,nonn
AUTHOR
N. J. A. Sloane, Feb 13 2002
STATUS
approved