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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 Adjacent sequences:  A006479 A006480 A006481 * A006483 A006484 A006485 KEYWORD nonn AUTHOR STATUS approved

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Last modified April 10 23:13 EDT 2021. Contains 342877 sequences. (Running on oeis4.)