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A012029
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E.g.f.: sech(sin(arctan(x))) (even powers only).
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1
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1, -1, 17, -721, 56993, -7232161, 1344866225, -344599447921, 116382225519425, -50097660050713921, 26773024797675332945, -17392081348966913859601, 13497082647397365780254177
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OFFSET
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0,3
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 0..50
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FORMULA
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a(n) ~ (-1)^n * 2^(2*n+5) * n^(2*n+1/2) * (Pi^2+4)^(n-1) / (exp(2*n) * Pi^(2*n+1/2)). - Vaclav Kotesovec, Nov 08 2013
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EXAMPLE
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sech(sin(arctan(x))) = 1 -1/2!*x^2 +17/4!*x^4 -721/6!*x^6 +56993/8!*x^8 ...
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MATHEMATICA
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With[{nn=30}, Take[CoefficientList[Series[Sech[Sin[ArcTan[x]]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Oct 03 2013 *)
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CROSSREFS
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Sequence in context: A309410 A201311 A012182 * A012193 A128274 A012085
Adjacent sequences: A012026 A012027 A012028 * A012030 A012031 A012032
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KEYWORD
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sign
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AUTHOR
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Patrick Demichel (patrick.demichel(AT)hp.com)
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STATUS
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approved
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