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Search: id:A131737
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| A131737 |
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Essentially even numbers followed by duplicated odd numbers. |
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+0
1
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| 0, 1, 1, 1, 2, 3, 3, 4, 5, 5, 6, 7, 7, 8, 9, 9, 10, 11, 11, 12, 13, 13, 14, 15, 15, 16, 17, 17, 18, 19, 19, 20, 21, 21, 22, 23, 23, 24, 25, 25, 26, 27, 27, 28, 29, 29, 30, 31, 31, 32, 33, 33, 34, 35, 35, 36, 37, 37, 38, 39, 39, 40, 41, 41, 42, 43, 43, 44, 45, 45, 46, 47, 47, 48, 49
(list; graph; listen)
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OFFSET
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0,5
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FORMULA
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a(0)=0. a(1)=a(2)=1. a(3n)=A005408(n-1). a(3n+1)=a(3n)+1. a(3n+2)=a(3n)+2, n>0.
O.g.f.: x(x^4+1)/((x-1)^2*(x^2+x+1)). a(n)=(2n-2-A057078(n))/3,n >1. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 16 2008
a(n)=(1/9)*Sum{k=0..n}{5*(k mod 3)+2*[(k+1) mod 3]-[(k+2) mod 3]}+[C(2*n,n) mod 2]+{C[(n+1)^2,n+3] mod 2}, with n>=0 [From Paolo P. Lava (ppl(AT)spl.at), Oct 07 2008]
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CROSSREFS
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Cf. A004396.
Sequence in context: A131138 A093878 A004396 this_sequence A066481 A121928 A067022
Adjacent sequences: A131734 A131735 A131736 this_sequence A131738 A131739 A131740
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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), Sep 19 2007
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EXTENSIONS
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Edited by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 16 2008
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