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A304454
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G.f. satisfies: A(x) = 1 / (1/x - 1 - A(A(x))), with A(0) = 0.
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0
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0, 1, 1, 2, 5, 15, 51, 191, 773, 3338, 15243, 73131, 366815, 1916260, 10394665, 58404853, 339223859, 2033188222, 12556915219, 79807729238, 521399203037, 3497978659977, 24076009827669, 169865542733652, 1227553152971419, 9079751310622581, 68692742886823205
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OFFSET
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0,4
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LINKS
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FORMULA
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EXAMPLE
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G.f. = x + x^2 + 2*x^3 + 5*x^4 + 15*x^5 + 51*x^6 + 191*x^7 + 773*x^8 + 3338*x^9 + ...
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MATHEMATICA
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a[ n_] := If[n < 0, 0, SeriesCoefficient[ Nest[ 1 / (1/x - 1 - (# /. x -> #)) &, O[x], Ceiling[n/2]], {x, 0, n}]];
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PROG
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(PARI) {a(n) = my(A); if( n<0, 0, A = O(x); forstep(k=1, n, 2, A = 1 / (1/x - 1 - subst(A, x, A))); polcoeff(A, n))};
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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