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Search: id:A052928
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| A052928 |
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The even numbers repeated. |
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+0
9
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| 0, 0, 2, 2, 4, 4, 6, 6, 8, 8, 10, 10, 12, 12, 14, 14, 16, 16, 18, 18, 20, 20, 22, 22, 24, 24, 26, 26, 28, 28, 30, 30, 32, 32, 34, 34, 36, 36, 38, 38, 40, 40, 42, 42, 44, 44, 46, 46, 48, 48, 50, 50, 52, 52, 54, 54, 56, 56, 58, 58, 60, 60, 62, 62, 64, 64, 66, 66, 68, 68, 70, 70, 72, 72
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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a(n) is also the binary rank of the complete graph K(n) [From Alessandro Cosentino (cosenal(AT)gmail.com), Feb 07 2009]
Its ordinal transform is A000034 [From Paolo P. Lava (ppl(AT)spl.at), Jun 25 2009]
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REFERENCES
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C. D. Godsil and G. Royle, Algebraic Graph Theory, Springer, 2001, pag.181 [From Alessandro Cosentino (cosenal(AT)gmail.com), Feb 07 2009]
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 914
Eric Weisstein's World of Mathematics, Wallis Formula
Eric Weisstein's World of Mathematics, Random Matrix
Eric Weisstein's World of Mathematics, Legendre-Gauss Quadrature
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FORMULA
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a(n)=2*Floor[n/2]. G.f.: 2/(-1+x)^2/(1+x).
Recurrence: {a(0)=2, a(n)+a(n+1)-4-2*n}. Also a(n) = n+3/2+1/2*(-1)^(-n)
a(n) = n + Sum{k=1..n, (-1)^k} - William A. Tedeschi (fynmun(AT)hotmail.com), Mar 20 2008
a(n)=2*n-a(n-1)-4 (with a(1)=0) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 21 2009]
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EXAMPLE
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For n=2,a(2)=2*2-0-4=0; n=3,a(3)=2*3-0-4=2; n=4,a(4)=2*4-2-4=2;n=5,a(5)=2*5-2-4=4 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 21 2009]
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MAPLE
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spec := [S, {S=Union(Sequence(Prod(Z, Z)), Prod(Sequence(Z), Sequence(Z)))}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
a:=n->add(1+(-1)^j, j=1..n):seq(a(n), n=0..94); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 13 2008]
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CROSSREFS
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Sequence in context: A061106 A161764 A131055 this_sequence A137501 A005186 A008642
Adjacent sequences: A052925 A052926 A052927 this_sequence A052929 A052930 A052931
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KEYWORD
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easy,nonn,new
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AUTHOR
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encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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EXTENSIONS
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More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jun 05 2000
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