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Search: id:A072851
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| A072851 |
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a(0) = 0, a(1) = a(2) = 1, a(n) = abs ( Sum{( - 1)^k*a(abs(n - k))*a(k), k=2..n-1}) |
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+0
3
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| 0, 1, 0, 1, 1, 1, 0, 1, 2, 1, 2, 3, 1, 3, 4, 1, 3, 5, 6, 1, 7, 29, 14, 41, 82, 39, 58, 109, 119, 1, 120, 579, 432, 675, 1320, 1325, 291, 259, 3332, 3657, 3724, 6015, 11114, 6465, 4325, 20433, 28884, 381, 5813, 91505, 96956, 70329, 106037, 260323, 260690, 78399
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OFFSET
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0,9
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COMMENT
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Derived from G.J. Chaitin's s formula.
Chaitin's expression is s(0)=0, s(1)=alpha, s(2)=1, s(n)=Sum{ s[n-k]*s[k], k=2..n-1}, but here it is made to alternate with the introduction of (-1)^k so that the numbers do not get large fast and alternate back and forth like a boustrophedon (A072231).
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REFERENCES
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G.J. Chaitin, Algorithmic Information Theory, Cambridge Press, 1987, page 169.
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MATHEMATICA
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s[n_Integer?Positive] := s[n]=Abs[Sum[(-1)^k*s[k-n]*s[k], {k, 2, n-1}]; s[0]=0; s[1]=1; s[2]=1; Table[ s[n], {n, 0, 200, 2}]
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CROSSREFS
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Sequence in context: A075106 A036995 A116908 this_sequence A103627 A080786 A036838
Adjacent sequences: A072848 A072849 A072850 this_sequence A072852 A072853 A072854
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KEYWORD
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nonn
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AUTHOR
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Roger L. Bagula (rlbagulatftn(AT)yahoo.com), Jul 25 2002
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EXTENSIONS
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Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Jul 29 2002
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