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Search: id:A154917
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| 0, 0, 1, 1, 3, 5, 11, 21, 43, 85, 171, 341, 683, 1365, 2731, 5461, 10923, 21845, 43691, 87381, 174763, 349525, 699051, 1398101, 2796203, 5592405, 11184811, 22369621, 44739243, 89478485, 178956971, 357913941, 715827883, 1431655765, 2863311531
(list; graph; listen)
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OFFSET
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0,5
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FORMULA
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a(n) = A001045(n-1), n>0.
a(n)+a(n+1) = A131577(n).
G.f.: x^2/((1+x)*(1-2*x)).
a(n)=(1/3)*[2^(n-1)-(-1)^(n-1)]-(1/2)*[C(2*n,n) mod 2], with n>=0 [From Paolo P. Lava (ppl(AT)spl.at), Jan 19 2009]
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CROSSREFS
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Sequence in context: A146042 A152046 A001045 this_sequence A167167 A077925 A084230
Adjacent sequences: A154914 A154915 A154916 this_sequence A154918 A154919 A154920
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KEYWORD
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nonn,easy,less
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AUTHOR
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Paul Curtz (bpcrtz(AT)free.fr), Jan 17 2009
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EXTENSIONS
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Notation cleaned up by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 07 2009
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