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A012029 E.g.f.: sech(sin(arctan(x))) (even powers only). 1
1, -1, 17, -721, 56993, -7232161, 1344866225, -344599447921, 116382225519425, -50097660050713921, 26773024797675332945, -17392081348966913859601, 13497082647397365780254177 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
LINKS
FORMULA
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
EXAMPLE
sech(sin(arctan(x))) = 1 -1/2!*x^2 +17/4!*x^4 -721/6!*x^6 +56993/8!*x^8 ...
MATHEMATICA
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 *)
CROSSREFS
Sequence in context: A309410 A201311 A012182 * A012193 A128274 A012085
KEYWORD
sign
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
STATUS
approved

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Last modified March 19 07:17 EDT 2024. Contains 370954 sequences. (Running on oeis4.)