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A107099
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G.f. satisfies A(A(x)) = x + 4*x^3, where A(x) = Sum_{n>=0} a(n)*x^(2*n+1).
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2
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1, 2, -6, 36, -266, 2028, -13596, 50088, 566694, -16598580, 232284876, -1912070088, 631155132, 239439857272, -2781218767224, -17362458802992, 795693633448710, -458070639409908, -335724554310292548, 4520379769156382616, 109439050270732883028, -3828757746830590219608
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OFFSET
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0,2
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COMMENTS
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Coefficients [x^n] A(x) = 0 (mod 3) except at n = 3^k (conjecture).
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LINKS
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EXAMPLE
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A(x) = 1*x + 2*x^3 - 6*x^5 + 36*x^7 - 266*x^9 + 2028*x^11 - 13596*x^13 +-...
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PROG
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(PARI) b(n) = local(A, B, F); F=x+4*x^3+x*O(x^n); A=F; if(n==0, 0, for(i=0, n, B=serreverse(A); A=(A+subst(B, x, F))/2); polcoeff(A, n, x));
a(n) = b(2*n+1);
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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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