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A273047
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E.g.f.: sqrt(-1+sqrt(1+3*cos(2*x)^2))/cos(2*x) [even terms only].
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1
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1, 1, 2, -149, -14743, -1291124, -75141463, 16904078101, 12079897715342, 5127055781374651, 1591577436442791797, 16734787827095948776, -636181884940159502862223, -835452999214833112556297399, -749352506033895636346796223718, -390445159197257248842601279581749
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OFFSET
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0,3
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COMMENTS
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The odd power terms are zero because the e.g.f. is even.
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LINKS
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EXAMPLE
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1 + 1*x^2/2! + 2*x^4/4! - 149*x^6/6! - ...
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PROG
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(PARI)
x = 'x + O('x^31);
v = Vec(serlaplace(sqrt(-1+sqrt(1+3*cos(2*x)^2))/cos(2*x)));
vector((#v+1)\2, k, v[2*k-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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