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A024236
Expansion of log(1+tan(x)*x)/2.
1
0, 1, -2, 48, -1040, 62720, -4314624, 498003968, -70081316864, 13529482592256, -3175495421788160, 933402531586899968, -326784893253162369024, 136568449424117316190208, -66517446960602151366164480
OFFSET
0,3
FORMULA
E.g.f. of aerated sequence: Sum(n>=0, a(n)*x^(2*n)/(2*n)!) = log(1+tan(x)*x)/2. - Robert Israel, Jun 29 2015
MAPLE
S:= series(log(1+tan(x)*x)/2, x, 101): seq(coeff(S, x, 2*j)*(2*j)!, j=0..50); # Robert Israel, Jun 29 2015
MATHEMATICA
With[{nn=30}, Take[CoefficientList[Series[Log[1+Tan[x]x]/2, {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jun 24 2018 *)
CROSSREFS
Cf. A009379.
Cf. A101921.
Sequence in context: A013523 A260846 A009670 * A119703 A012803 A135394
KEYWORD
sign
AUTHOR
EXTENSIONS
Extended with signs, Mar 1997
Previous Mathematica program replaced by Harvey P. Dale, Jun 24 2018
STATUS
approved