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A293192 a(n) = n! * [x^n] exp(n*arctan(x)). 1
1, 1, 4, 21, 128, 745, 1440, -89075, -3031040, -76951215, -1784742400, -39056351675, -785147904000, -12815410658375, -64977212518400, 8229576066616125, 587339977981952000, 29185361934747006625, 1256364637107240960000, 48860370609512175371125, 1686271331087959982080000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..20.

MATHEMATICA

Table[n! SeriesCoefficient[Exp[n ArcTan[x]], {x, 0, n}], {n, 0, 20}]

Table[n! SeriesCoefficient[Exp[n Sum[(-1)^k x^(2 k + 1)/(2 k + 1), {k, 0, Infinity}]], {x, 0, n}], {n, 0, 20}]

CROSSREFS

Cf. A002019.

Sequence in context: A007345 A255673 A099250 * A232956 A234268 A111177

Adjacent sequences:  A293189 A293190 A293191 * A293193 A293194 A293195

KEYWORD

sign

AUTHOR

Ilya Gutkovskiy, Oct 02 2017

STATUS

approved

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Last modified February 20 19:06 EST 2018. Contains 299382 sequences. (Running on oeis4.)