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A081367
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E.g.f.: exp(2*x)/sqrt(1-2*x).
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10
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1, 3, 11, 53, 345, 2947, 31411, 400437, 5927921, 99816515, 1882741659, 39310397557, 899919305929, 22410922177347, 603120939234755, 17441737474345973, 539390080299331809, 17762381612118471043
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = U(1/2,3/2+n,1)*2^n, where U is the confluent hypergeometric Kummer function U. - John M. Campbell, May 04 2011
D-finite with recurrence: a(n) = (2*n+1)*a(n-1) - 4*(n-1)*a(n-2). - Vaclav Kotesovec, Oct 13 2012
G.f.: W(0)/(1-2*x), where W(k) = 1 - x*(k+1)/(x*(k+1) - (1-2*x)/W(k+1) ); (continued fraction). - Sergei N. Gladkovskii, Nov 03 2014
a(n) = 2^n * hypergeom([1/2,-n],[],-1).
G.f. satisfies (1-3*x+4*x^2)*g(x) + (-2*x^2+4*x^3)*g'(x) = 1. (End)
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MAPLE
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F:= gfun:-rectoproc({a(n) = (2*n+1)*a(n-1) - 4*(n-1)*a(n-2), a(0)=1, a(1)=3}, a(n), remember):
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MATHEMATICA
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Table[HypergeometricU[1/2, 3/2 + n, 1]*2^n, {n, 0, 20}]
With[{nn=20}, CoefficientList[Series[Exp[2x]/Sqrt[1-2x], {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Mar 20 2015 *)
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PROG
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(PARI) a(n)=n!*polcoeff(exp(2*x)/sqrt(1-2*x)+O(x^(n+1)), n)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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