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A157316
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G.f.: A(x) = tanh( Sum_{n>=0} 2^((2n+1)^2) * x^(2n+1)/(2n+1) ), with zero terms omitted.
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0
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OFFSET
| 0,1
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COMMENTS
| Compare g.f. to the expansion of the inverse tanh of x:
atanh(x) = log((1+x)/(1-x))/2 = x + x^3/3 + x^5/5 + x^7/7 +...
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EXAMPLE
| G.f.: A(x) = 2*x + 168*x^3 + 6710208*x^5 + 80421395017344*x^7 +...
atanh(A(x)) = 2*x + 2^9*x^3/3 + 2^25*x^5/5 + 2^49/7*x^7 +...
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PROG
| (PARI) {a(n)=polcoeff(tanh(sum(m=0, n, 2^((2*m+1)^2)*x^(2*m+1)/(2*m+1))+O(x^(2*n+2))), 2*n+1)}
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CROSSREFS
| Cf. A157315.
Sequence in context: A142602 A200042 A005020 * A007760 A051030 A139935
Adjacent sequences: A157313 A157314 A157315 * A157317 A157318 A157319
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KEYWORD
| nonn
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AUTHOR
| Paul D. Hanna (pauldhanna(AT)juno.com), Mar 19 2009
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