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 A216409 E.g.f.: Series_Reversion( x*Cw(x) ) where Cw(x) = Sum_{n>=0} (-1)^n*(2*n+1)^(2*n-1)*x^(2*n)/(2*n)!. 2
 1, 9, 185, 6769, 384849, 31247161, 3421948361, 485057489505, 86270172949025, 18789108183911401, 4913945007420622425, 1518613513007413125073, 547156929866111948071025, 227227144424871839232479769, 107701858026047543489146771049 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA E.g.f. A(x) satisfies: (1) Sum_{n>=0} (-1)^n*(2*n+1)^(2*n)*A(x)^(2*n+1)/(2*n+1)! = x. (2) A( atan(Sw(x)/Cw(x)) ) = x where Sw(x) = Sum_{n>=0} (-1)^n*(2*n+2)^(2*n) * x^(2*n+1)/(2*n+1)!. EXAMPLE E.g.f.: A(x) = x + 9*x^3/3! + 185*x^5/5! + 6769*x^7/7! + 384849*x^9/9! +... such that A(x*Cw(x)) = x where Cw(x) = 1 - 3*x^2/2! + 125*x^4/4! - 16807*x^6/6! + 4782969*x^8/8! -+...+ (-1)^n*(2*n+1)^(2*n-1)*x^(2*n)/(2*n)! +... Related expansion: Sw(x) = x - 16*x^3/3! + 1296*x^5/5! - 262144*x^7/7! + 100000000*x^9/9! -+...+ (-1)^n*(2*n+2)^(2*n)*x^(2*n+1)/(2*n+1)! +... where Cw(x) + I*Sw(x) = LambertW(-I*x)/(-I*x). PROG (PARI) {a(n)=local(Cw=sum(m=0, n, (-1)^m*(2*m+1)^(2*m-1)*x^(2*m)/(2*m)!) +x*O(x^n)); n!*polcoeff(serreverse(x*Cw), n)} for(n=1, 20, print1(a(2*n-1), ", ")) \\ print only odd-indexed terms CROSSREFS Cf. A215890, A138734, A215880, A215881, A215882, A216143. Sequence in context: A319798 A300598 A189803 * A171194 A196297 A274781 Adjacent sequences:  A216406 A216407 A216408 * A216410 A216411 A216412 KEYWORD nonn AUTHOR Paul D. Hanna, Sep 06 2012 STATUS approved

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Last modified September 23 11:53 EDT 2020. Contains 337310 sequences. (Running on oeis4.)