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Search: id:A054644
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| A054644 |
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Number of labeled pure 2-complexes on n nodes with 3 2-simplexes. |
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+0
1
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| 4, 120, 1140, 6545, 27720, 95284, 280840, 735130, 1750540, 3858140, 7971964, 15596035, 29112720, 52174360, 90223760, 151173044, 246274580, 391222160, 607525380, 924205205, 1379864024, 2025189100, 2925954200, 4166590350
(list; graph; listen)
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OFFSET
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4,1
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FORMULA
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a(n)=binomial(binomial(n, 3), 3)=4*binomial(n, 4)+100*binomial(n, 5)+480*binomial(n, 6)+945*binomial(n, 7)+840*binomial(n, 8)+280*binomial(n, 9)=n*(n-1)*(n-2)*(n-3)*(n^2+2)*(n^3-3*n^2+2*n-12)/1296.
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CROSSREFS
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Cf. A054563.
Sequence in context: A146508 A096464 A064204 this_sequence A006434 A002702 A068204
Adjacent sequences: A054641 A054642 A054643 this_sequence A054645 A054646 A054647
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KEYWORD
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easy,nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)eunet.rs), Apr 15 2000
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EXTENSIONS
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More terms from James A. Sellers (sellersj(AT)math.psu.edu), Apr 16 2000
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