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 A072851 a(0) = 0, a(1) = a(2) = 1, a(n) = abs ( Sum{( - 1)^k*a(abs(n - k))*a(k), k=2..n-1}) 4
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,9 COMMENTS 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). REFERENCES G.J. Chaitin, Algorithmic Information Theory, Cambridge Press, 1987, page 169. LINKS MATHEMATICA 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}] CROSSREFS Sequence in context: A116908 A265146 A325537 * A246688 A103627 A344088 Adjacent sequences:  A072848 A072849 A072850 * A072852 A072853 A072854 KEYWORD nonn AUTHOR Roger L. Bagula, Jul 25 2002 EXTENSIONS Edited and extended by Robert G. Wilson v, Jul 29 2002 STATUS approved

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Last modified June 15 12:29 EDT 2021. Contains 345048 sequences. (Running on oeis4.)