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Search: id:A058396
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| A058396 |
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Expansion of (1-x)^3/(1-2x)^3. |
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+0
10
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| 1, 3, 9, 25, 66, 168, 416, 1008, 2400, 5632, 13056, 29952, 68096, 153600, 344064, 765952, 1695744, 3735552, 8192000, 17891328, 38928384, 84410368, 182452224, 393216000, 845152256, 1811939328, 3875536896, 8271167488, 17616076800
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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If X_1,X_2,...,X_n are 2-blocks of a (2n+3)-set X then, for n>=1, a(n+1) is the number of (n+2)-subsets of X intersecting each X_i, (i=1,2,...,n). - Milan R. Janjic (agnus(AT)blic.net), Nov 18 2007
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LINKS
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Milan Janjic, Two Enumerative Functions
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FORMULA
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a(n) =(n+2)*(n+7)*2^(n-4) for n>0
a(n)=sum{k=0..floor((n+2)/2), C(n+2, 2k)k(k+1)/2 } - Paul Barry (pbarry(AT)wit.ie), May 15 2003
Binomial transform of quarter squares A002620 (without leading zeros). - Paul Barry (pbarry(AT)wit.ie), May 27 2003
a(n)=sum{k=0..n, C(n, k)Floor((k+2)^2/4) } - Paul Barry (pbarry(AT)wit.ie), May 27 2003
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MATHEMATICA
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CoefficientList[ Series[(1 - x)^3/(1 - 2x)^3, {x, 0, 28}], x] (from Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 28 2005)
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CROSSREFS
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Cf. A045623. A diagonal of A058395.
Cf. A001793.
Sequence in context: A002064 A129589 A096322 this_sequence A006809 A081663 A106514
Adjacent sequences: A058393 A058394 A058395 this_sequence A058397 A058398 A058399
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KEYWORD
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nonn
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AUTHOR
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Henry Bottomley (se16(AT)btinternet.com), Nov 24 2000
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EXTENSIONS
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More terms from Paul Barry (pbarry(AT)wit.ie), May 27 2003
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