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%I #22 Mar 17 2023 14:41:37
%S 1,0,-1,3,-9,30,-109,420,-1685,6960,-29391,126291,-550359,2426502,
%T -10803801,48507843,-219377949,998436792,-4569488371,21016589073,
%U -97090411019,450314942682,-2096122733211,9788916220518
%N Row sums of triangle A091698.
%C Hankel transform is (-1)^n. - _Paul Barry_, Jun 17 2010
%H Vincenzo Librandi, <a href="/A091699/b091699.txt">Table of n, a(n) for n = 0..200</a>
%F G.f.: A(x) = 2/(3+3*x - sqrt(1+6*x+5*x^2)). - _Paul D. Hanna_, Feb 23 2004
%F Conjecture: 2*n*a(n) + (13*n-16)*a(n-1) + 4*(4*n-7)*a(n-2) + 5*(n-2)*a(n-3) = 0. - _R. J. Mathar_, Nov 24 2012
%F a(n) ~ (-1)^(n+1) * 5^(n+3/2) / (72 * sqrt(Pi) * n^(3/2)). - _Vaclav Kotesovec_, Feb 12 2014
%t CoefficientList[Series[2/(3+3*x-Sqrt[1+6*x+5*x^2]), {x, 0, 20}], x] (* _Vaclav Kotesovec_, Feb 12 2014 *)
%o (PARI) a(n)=polcoeff(2/(3+3*x-sqrt(1+6*x+5*x^2+x*O(x^n))),n,x) \\ _Paul D. Hanna_
%Y Cf. A091698.
%K sign
%O 0,4
%A _Christian G. Bower_, Jan 29 2004
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