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Search: id:A054558
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| A054558 |
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Number of labeled pure 2-complexes on n nodes (0-simplexes) with 5 2-simplexes and 9 1-simplexes. |
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1
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| 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; listen)
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OFFSET
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5,1
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COMMENT
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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.
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REFERENCES
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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.
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FORMULA
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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
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CROSSREFS
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Cf. A054557.
Sequence in context: A008889 A063829 A140671 this_sequence A073614 A088361 A135968
Adjacent sequences: A054555 A054556 A054557 this_sequence A054559 A054560 A054561
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KEYWORD
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nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)Eunet.yu), Apr 10 2000
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