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 A123686 E.g.f.: (1-x^4)^(-1/2)*exp(x^2/(1-x^2))*BesselI(0,x^2/(x^2-1)) (since this is an even function, we do not give the intercalating 0's). 2
 1, 2, 54, 2460, 239190, 33124140, 6896500380, 1879519201560, 674900483206950, 300426422192196300, 164868151446145847700, 108046627817926248851400, 83890281074290204071858300, 75722368306901033144261835000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Arises in the normal ordering of functions of a*(a+)*a, where a and a+ are the boson annihilation and creation operators, respectively. LINKS G. C. Greubel, Table of n, a(n) for n = 0..220 FORMULA From Vaclav Kotesovec, Nov 13 2017: (Start) Recurrence: n*a(n) = 2*(2*n - 1)*(3*n - 2)*a(n-1) + 4*(n-1)^2*(2*n - 3)*(2*n - 1)*(2*n + 1)*a(n-2) + 8*(n-2)^2*(n-1)*(2*n - 5)*(2*n - 3)*(2*n - 1)*a(n-3) - 16*(n-3)^2*(n-2)^2*(n-1)*(2*n - 7)*(2*n - 5)*(2*n - 3)*(2*n - 1)*a(n-4). a(n) ~ 2^(2*n - 3/4) * exp(2*sqrt(2*n) - 2*n -1) * n^(2*n - 1/4) / sqrt(Pi) * (1 + 91/(48*sqrt(2*n))). (End) MAPLE G:=(1-x^4)^(-1/2)*exp(x^2/(1-x^2))*BesselI(0, x^2/(x^2-1)): Gser:=series(G, x=0, 40): seq((2*n)!*coeff(Gser, x, 2*n), n=0..15); # Emeric Deutsch, Oct 31 2006 MATHEMATICA With[{nmax = 50}, CoefficientList[Series[(1 - x^4)^(-1/2)*Exp[x^2/(1 - x^2)]*BesselI[0, x^2/(x^2 - 1)], {x, 0, nmax}], x]*Range[0, nmax]!][[;; ;; 2 ]] (* G. C. Greubel, Oct 18 2017 *) CROSSREFS Cf. A123510, A123511, A123512, A123525. Sequence in context: A157058 A305693 A071798 * A122418 A069788 A283678 Adjacent sequences:  A123683 A123684 A123685 * A123687 A123688 A123689 KEYWORD nonn AUTHOR Karol A. Penson, Oct 06 2006 EXTENSIONS More terms from Emeric Deutsch, Oct 31 2006 STATUS approved

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Last modified October 14 16:48 EDT 2019. Contains 328022 sequences. (Running on oeis4.)