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 A012264 Number of real roots of x - x^3/3! + x^5/5! - ... + (-1)^n*x^(2n+1)/(2n+1)!. 2
 1, 3, 1, 3, 5, 3, 5, 7, 5, 7, 5, 7, 9, 7, 9, 7, 9, 11, 9, 11, 13, 11, 13, 11, 13, 15, 13, 15, 17, 15, 17, 15, 17, 19, 17, 19, 17, 19, 21, 19, 21, 23, 21, 23, 21, 23, 25, 23, 25, 23, 25, 27, 25, 27, 29, 27, 29, 27, 29, 31, 29, 31, 33 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 REFERENCES James Propp, posting to math-fun mailing list May 30 1997. LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..200 MAPLE Digits := 25: t1 := 0: for k from 1 by 2 to 51 do t1 := t1+(-1)^( (k-1)/2 )*x^k/k!; print(nops([ fsolve(t1*k!) ])); od: MATHEMATICA f[n_] := Sum[ (-1)^k*x^(2k+1)/(2k+1)!, {k, 0, n}]; a[n_] := CountRoots[f[n], x]; Table[a[n], {n, 0, 62}] (* Jean-François Alcover, Sep 13 2012 *) CROSSREFS Cf. A012265. Sequence in context: A263051 A284130 A005474 * A063198 A122582 A173039 Adjacent sequences:  A012261 A012262 A012263 * A012265 A012266 A012267 KEYWORD nonn,nice AUTHOR EXTENSIONS More terms from James A. Sellers STATUS approved

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Last modified September 26 02:39 EDT 2020. Contains 337346 sequences. (Running on oeis4.)