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Search: id:A052953
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| A052953 |
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A simple regular expression. |
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+0
7
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| 2, 2, 4, 6, 12, 22, 44, 86, 172, 342, 684, 1366, 2732, 5462, 10924, 21846, 43692, 87382, 174764, 349526, 699052, 1398102, 2796204, 5592406, 11184812, 22369622, 44739244, 89478486, 178956972, 357913942, 715827884, 1431655766, 2863311532
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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a(n) = sum of absolute values of terms in the (n+1)-th row of the triangle in A108561; - Reinhard Zumkeller (reinhard.zumkeller(AT)lhsystems.com), Jun 10 2005
a(n) = A078008(n+1) + 2*(1 + n mod 2). - Reinhard Zumkeller (reinhard.zumkeller(AT)lhsystems.com), Jun 10 2005
Essentially the same as A128209. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jun 14 2008
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 1024
Zerinvary Lajos, Sage Notebooks
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FORMULA
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G.f.: -2*(-1+x+x^2)/(-1+x+2*x^2)/(-1+x)
Recurrence: {a(2)=4, a(1)=2, a(0)=2, -2*a(n)-a(n+1)+a(n+2)+2}
1+Sum(1/9*(1+4*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z+2*_Z^2))
a(2n)=2*a(n-1)-2, a(2n+1)=2*a(2n). - Lee Hae-hwang (mathmaniac(AT)empal.com), Oct 11 2002
a(n)=A001045(n+1)+1; a(n)=(2^(n+1)-(-1)^(n+1))/3+1. - Paul Barry (pbarry(AT)wit.ie), May 24 2004
Is it true that a(n)=A001045(n+1)+1? - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jul 06 2008
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MAPLE
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spec := [S, {S=Union(Sequence(Union(Prod(Union(Z, Z), Z), Z)), Sequence(Z))}, unlabeled ]: seq(combstruct[count ](spec, size=n), n=0..20);
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PROGRAM
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sage: from sage.combinat.sloane_functions import recur_gen2 sage: it = recur_gen2(1, 1, 1, 2) sage: [it.next()+1 for i in xrange(0, 34)] - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jul 06 2008
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CROSSREFS
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Apart from initial term, equals A026644(n+1) + 2.
Sequence in context: A003000 A122536 A128209 this_sequence A074028 A061894 A116684
Cf. A001045.
Adjacent sequences: A052950 A052951 A052952 this_sequence A052954 A052955 A052956
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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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