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A054558 Number of labeled pure 2-complexes on n nodes (0-simplexes) with 5 2-simplexes and 9 1-simplexes. 1
150, 960, 3605, 10360, 25200, 54600, 108570, 201960, 356070, 600600, 975975, 1536080, 2351440, 3512880, 5135700, 7364400, 10377990, 14395920, 19684665, 26565000, 35420000, 46703800, 60951150, 78787800, 100941750, 128255400 (list; graph; refs; listen; history; text; internal format)
OFFSET
5,1
COMMENTS
Number of {T_1,T_2,...,T_k} where T_i, i=1..k are 3-subsets of an n-set such that {D | D is 2-subset of T_i for some i=1..k} has l elements; k=5, l=9.
REFERENCES
V. Jovovic, On the number of two-dimensional simplicial complexes (in Russian), Metody i sistemy tekhnicheskoy diagnostiki, Vypusk 16, Mezhvuzovskiy zbornik nauchnykh trudov, Izdatelstvo Saratovskogo universiteta, 1991.
LINKS
FORMULA
a(n) = 150*C(n,5) +60*C(n,6) +35*C(n,7) = n*(n-1)*(n-2)*(n-3)*(n-4)*(n^2+n+150)/144.
G.f.: 5*x^5*(30-48*x+25*x^2)/(1-x)^8. - Colin Barker, Jun 21 2012
MAPLE
A054558:=n->n*(n-1)*(n-2)*(n-3)*(n-4)*(n^2+n+150)/144; seq(A054558(n), n=5..30); # Wesley Ivan Hurt, Apr 29 2014
MATHEMATICA
Table[n*(n - 1)*(n - 2)*(n - 3)*(n - 4)*(n^2 + n + 150)/144, {n, 5, 30}] (* Wesley Ivan Hurt, Apr 29 2014 *)
CROSSREFS
Cf. A054557.
Sequence in context: A273322 A206066 A140671 * A250544 A251801 A211554
KEYWORD
nonn,easy
AUTHOR
Vladeta Jovovic, Apr 10 2000
STATUS
approved

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Last modified April 24 04:14 EDT 2024. Contains 371918 sequences. (Running on oeis4.)