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Search: id:A104749
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| A104749 |
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Expansion of a parametrization of x^2-y+y^2=0. |
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+0
1
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| 1, -2, -6, 20, -26, 324, 932, -3864, -12282, -8812, 123596, -1011048, 1302748, -9066968, -11700216, 327436496, 500340678, 4725531060, 3741191612, -11250963784, -147523219212, -1497706973320, -7306482940296, -675852523344, 10735087541148
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OFFSET
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0,2
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FORMULA
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Given g.f. A(x), B(x)=x*A(x^2/4) satisfies 0=f(B(x), B(x^2)) where f(u, v)=u^2-v+v^2
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EXAMPLE
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Series is x - 1/2*x^3 - 3/8*x^5 + 5/16*x^7 - 13/128*x^9 + ...
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PROGRAM
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(PARI) {a(n)=local(A, m); if(n<0, 0, A=1+O(x); m=1; while(m<=n, m*=2; A=subst(A, x, 4*x^2); A=sqrt(A-4*x*A^2)); polcoeff(A, n))}
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CROSSREFS
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Sequence in context: A156269 A128447 A032622 this_sequence A062281 A131441 A035142
Adjacent sequences: A104746 A104747 A104748 this_sequence A104750 A104751 A104752
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KEYWORD
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sign
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AUTHOR
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Michael Somos, Mar 24 2005
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