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Search: id:A106400
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| A106400 |
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Thue-Morse sequence: let A_k denote the first 2^k terms; then A_0 = 1 and for k >= 0, A_{k+1} = A_k B_k, where B_k is obtained from A_k by interchanging 1's and -1's. |
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4
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| 1, -1, -1, 1, -1, 1, 1, -1, -1, 1, 1, -1, 1, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1, 1, 1, -1, -1, 1, -1, 1, 1, -1, -1, 1, 1, -1, 1, -1, -1, 1, 1, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1, 1, -1, 1, 1, -1, -1, 1, 1, -1, 1, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1, 1, 1, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1, 1, -1, 1, 1, -1, -1, 1, 1, -1, 1, -1, -1, 1, 1, -1, -1, 1, -1, 1
(list; graph; listen)
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OFFSET
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0,1
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LINKS
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Joerg Arndt, Fxtbook
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FORMULA
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G.f. A(x) satisfies 0=f(A(x), A(x^2), A(x^4)) where f(u, v, w)=v^3-2uvw+u^2w.
G.f. A(x) satisfies 0=f(A(x), A(x^2), A(x^3), A(x^6)) where f(u1, u2, u3, u6)=u6*u1^3 - 3*u6*u2*u1^2 + 3*u6*u2^2*u1 - u3*u2^3.
Euler transform of sequence b(n) where b(2^k)=-1 and zero otherwise.
G.f.: Product_{k>=0} (1-x^(2^k)) = A(x) = (1-x)A(x^2).
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PROGRAM
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(PARI) {a(n)=if(n<1, n>=0, a(n\2)*(-1)^(n%2))}
(PARI) {a(n)=local(A, m); if(n<1, n==0, m=1; A=1+O(x); while(m<=n, m*=2; A=subst(A, x, x^2)*(1-x)); polcoeff(A, n))}
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CROSSREFS
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Cf. a(n)=(-1)^A010060(n).
Convolution inverse of A018819.
Sequence in context: A000012 A008836 A064179 this_sequence A112865 A121241 A122188
Adjacent sequences: A106397 A106398 A106399 this_sequence A106401 A106402 A106403
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KEYWORD
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sign
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AUTHOR
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Michael Somos, May 02 2005
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