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A130169 a(1) = 1; for n>1, a(n) = (c(n) + c(n+1))/2, where c(n) = A130168(n). 2

%I

%S 1,2,9,63,621,8127,135729,2810403,70558101,2109957687,74061977049,

%T 3014272078443,140764140297981,7474792551154047,447790997859123969,

%U 30053688313164013683,2245843775591721612261,185829940905166760571207,16941047558158020804504489

%N a(1) = 1; for n>1, a(n) = (c(n) + c(n+1))/2, where c(n) = A130168(n).

%D Hippolyte Dellac, Note sur l'élimination, méthode de parallélogramme, Annales de la Faculté des Sciences de Marseille, XI (1901), 141-164.

%F G.f.: (1+x)^2/(3*x^3)*Q(0) + (x^3 - 5*x^2 - 5*x - 2)/(6*x^3), where Q(k) = 1 - x*(k+1)^2/( x*(k+1)^2 - 2/(1 - x*(k+1)^2/( x*(k+1)^2 - 2/Q(k+1) ))); (continued fraction). - _Sergei N. Gladkovskii_, Oct 22 2013

%Y Cf. A000366, A130168.

%K nonn

%O 1,2

%A _Don Knuth_, Aug 02 2007

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Last modified August 9 22:52 EDT 2020. Contains 336335 sequences. (Running on oeis4.)