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A193527
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G.f. A(x) satisfies 0 = f(A(x), A(x^2)) where f(u, v) = u * (u - 2) - (v + 2).
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0
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1, 1, 2, 0, -1, 0, 2, 0, -5, 0, 12, 0, -30, 0, 82, 0, -233, 0, 668, 0, -1949, 0, 5802, 0, -17503, 0, 53302, 0, -163783, 0, 507418, 0, -1582869, 0, 4966790, 0, -15667573, 0, 49658264, 0, -158059506, 0, 505013014, 0, -1619144976, 0, 5207596574
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OFFSET
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-1,3
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LINKS
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FORMULA
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a(2*n) = 0 unless n=0. a(n) = A107088(n+1) unless n=0. a(2*n - 1) = A107087(n).
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EXAMPLE
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1/x + 1 + 2*x - x^3 + 2*x^5 - 5*x^7 + 12*x^9 - 30*x^11 + 82*x^13 - ...
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PROG
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(PARI) {a(n) = local(A, m); if( n<-1, 0, if( n%2 == 0, n==0, A = 1 + O(x); m=1; while( 2*m <= n+1, A = sqrt(4*x + subst(A, x, x^2)); m*=2); polcoeff(A, (n+1)/2)))}
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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