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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
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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; refs; listen; history; internal format)
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OFFSET
| 4,1
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FORMULA
| 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.
G.f.: x^4*(4+80*x+120*x^2+65*x^3+10*x^4+x^5)/(1-x)^10. - Colin Barker, Jan 19 2012
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MATHEMATICA
| Table[Binomial[Binomial[n, 3], 3], {n, 4, 60}] [From Vladimir Orlovsky (4vladimir(AT)gmail.com), May 30 2010]
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PROG
| (Other) sage: [(binomial(binomial(n, 3), 3)) for n in xrange(4, 28)] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Nov 30 2009]
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CROSSREFS
| Cf. A054563.
Sequence in context: A146508 A096464 A064204 * A006434 A002702 A068204
Adjacent sequences: A054641 A054642 A054643 * A054645 A054646 A054647
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KEYWORD
| nonn,easy
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AUTHOR
| Vladeta Jovovic (vladeta(AT)eunet.rs), Apr 15 2000
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EXTENSIONS
| More terms from James A. Sellers (sellersj(AT)math.psu.edu), Apr 16 2000
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