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%I #8 Nov 03 2015 09:37:17
%S 1,7,21,66,715,2431,8398,29393,104006,371450,1337220,17678835,
%T 64822395,238819350,883631595,3282060210,12233133510,45741281820,
%U 171529806825,644952073662,2430973200726,9183676536076,34766775458002
%N Even Catalan numbers divided by 2.
%F a(n) = A152670(n)/2.
%t Select[CatalanNumber[Range[30]], EvenQ]/2 (* _Vladimir Reshetnikov_, Nov 02 2015 *)
%o (PARI) lista(nn) = for (n=1, nn, if (((c=binomial(2*n,n)/(n+1)) % 2) == 0, print1(c/2, ", "))); \\ _Michel Marcus_, Nov 02 2015
%Y Cf. A000108, A152670.
%K easy,nonn
%O 1,2
%A _Omar E. Pol_, Dec 10 2008