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Number of Catalan objects fixed by two-fold application of the Catalan bijections A057511/A057512 (Deep rotation of general parenthesizations/plane trees).
8

%I #4 Oct 17 2015 08:36:23

%S 1,1,2,5,11,26,66,161,420,1093,2916,7819,21304,58321,161233,448090,

%T 1253252,3521389,9941693,28175716,80152141,228747967,654817275,

%U 1879602446,5408974390,15601662378,45098766532,130624550412

%N Number of Catalan objects fixed by two-fold application of the Catalan bijections A057511/A057512 (Deep rotation of general parenthesizations/plane trees).

%F a(n) = A079216(n, 2)

%p A079223 := n -> A079216bi(n,2);

%Y The second row of A079216. The leftmost edge of the triangle A079218 and also its row sums shifted by one. Occurs for first time in A073202 as row 245. Cf. A057546, A079224, A079225, A079226, A079227.

%K nonn

%O 0,3

%A _Antti Karttunen_ Jan 03 2002