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A006482 Euler characteristics of polytopes.
(Formerly M1357)
0
1, 1, 0, 2, 5, 9, 14, 20, 69, 125, 209, 329, 923, 1715, 3002, 5004, 12869, 24309, 43757, 75581, 184755, 352715, 646645, 1144065, 2704155, 5200299, 9657699, 17383859, 40116599 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
H. Hadwiger and P. Mani, On polyhedra with extremal Euler characteristic, J. Combin. Theory, A 17 (1974), 345-349.
FORMULA
Numbers suggest that for n>3, a(n) = C(n, [n/2])-1 if (n mod 4)=0 or 1 and C(n, [n/2]-1)-1 otherwise. - Ralf Stephan, Jun 07 2005
PROG
(PARI) a(n)=if(n<3, (n==0||n==1), if(n<4, 2, -1+if(n%4==0||n%4==1, binomial(n, n\2), binomial(n, n\2-1)))) \\ Ralf Stephan, Jun 07 2005
CROSSREFS
Sequence in context: A112873 A048093 A024669 * A191170 A191123 A152888
KEYWORD
nonn
AUTHOR
STATUS
approved

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Last modified March 28 09:04 EDT 2024. Contains 371240 sequences. (Running on oeis4.)