(MAGMAMagma) m:=25; R<x>:=PowerSeriesRing(Rationals(), m); Coefficients(R!((1+x-x^2-Sqrt(1-10*x-x^2+10*x^3+x^4))/(6*x*(1-x^2)))) // G. C. Greubel, Apr 30 2018
(MAGMAMagma) m:=25; R<x>:=PowerSeriesRing(Rationals(), m); Coefficients(R!((1+x-x^2-Sqrt(1-10*x-x^2+10*x^3+x^4))/(6*x*(1-x^2)))) // G. C. Greubel, Apr 30 2018
reviewed
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reviewed
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proposed
G.f.: (1+x-x^2-sqrt(1-10x10*x-x^2+10x10*x^3+x^4))/(6x6*x*(1-x^2));.
a(n) = sumSum_{k=0..floor(n/2), } C(n-k,k)*A107841(n-2k2*k)}.
(PARI) x='x+O('x^30); Vec((1+x-x^2-sqrt(1-10*x-x^2+10*x^3+x^4))/(6*x*(1-x^2))) \\ G. C. Greubel, Apr 30 2018
(MAGMA) m:=25; R<x>:=PowerSeriesRing(Rationals(), m); Coefficients(R!((1+x-x^2-Sqrt(1-10*x-x^2+10*x^3+x^4))/(6*x*(1-x^2)))) // G. C. Greubel, Apr 30 2018
approved
editing
reviewed
approved
proposed
reviewed
editing
proposed
ConjectureRecurrence: n*(n+1)*a(n) = (n-5)*a(n-6) + 5*(2*n-17)*a(n-15) -n* (2*n-17)*a(n-24) +- 20*n*(n-2)*a(n-3) +n* (2*n-71)*a(n-42) -+ 5*n*(2*n-7)*a(n-5) -n*(n-51)*a(n-61) =0. - R. J. Mathar, Jul 24 2012, simplified by _Fung Lam_, Jan 27 2014
Recurrence: (n+1)*a(n) = (n-5)*a(n-6) + 5*(2*n-7)*a(n-5) - (2*n-7)*a(n-4) - 20*(n-2)*a(n-3) + (2*n-1)*a(n-2) + 5*(2*n-1)*a(n-1). - Fung Lam, Jan 27 2014 (Identical to Mathar's except multiplication factor n.)
a(n) ~ r*(r+10) * sqrt(10*r^3-2*r^2-30*r+4) / (12 * sqrt(Pi) * n^(3/2) * r^(n+1)), where r = 1 / (5/2 + sqrt(6) + 1/2*sqrt(53+20*sqrt(6))) = 0.100010105114224353... - Vaclav Kotesovec, Feb 27 2014
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editing