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Search: id:A052535
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| A052535 |
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A simple regular expression. |
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+0
2
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| 1, 1, 2, 4, 7, 14, 26, 50, 95, 181, 345, 657, 1252, 2385, 4544, 8657, 16493, 31422, 59864, 114051, 217286, 413966, 788674, 1502555, 2862617, 5453761, 10390321, 19795288, 37713313, 71850128, 136886433, 260791401, 496850954, 946583628
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Diagonal sums of A054142. - Paul Barry (pbarry(AT)wit.ie), Jan 21 2005
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 465
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FORMULA
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G.f.: -(-1+x^2)/(1-2*x^2+x^4-x)
Recurrence: {a(1)=1, a(0)=1, a(3)=4, a(2)=2, a(n)-2*a(n+2)-a(n+3)+a(n+4)}
Sum(-1/283*(-112*_alpha+48*_alpha^3-9*_alpha^2-27)*_alpha^(-1-n), _alpha=RootOf(1-2*_Z^2+_Z^4-_Z))
a(n)=sum{k=0..floor(n/2), binomial(2n-3k, k)}. - Paul Barry (pbarry(AT)wit.ie), Jan 21 2005
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Union(Z, Sequence(Prod(Z, Z)))))}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A076739 A017996 A024502 this_sequence A027988 A005594 A123196
Adjacent sequences: A052532 A052533 A052534 this_sequence A052536 A052537 A052538
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KEYWORD
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easy,nonn
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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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