%I A023428
%S A023428 1,1,1,1,1,1,2,4,7,11,17,27,45,77,132,224,378,640,
%T A023428 1093,1881,3250,5622,9732,16874,29332,51126,89313,
%U A023428 156283,273842,480474,844220,1485472,2617335,4617243
%N A023428 Generalized Catalan Numbers.
%t A023428 Clear[ a ]; a[ 0 ]=1; a[ n_Integer ] := a[ n ]=a[ n-1 ]+Sum[ a[ k ]*a[ 
               n-4-k ], {k, 2, n-4} ];
%Y A023428 Cf. A000108, A001006, A004148, A006318.
%Y A023428 Sequence in context: A005252 A023430 A023429 this_sequence A093911 A152398 
               A023427
%Y A023428 Adjacent sequences: A023425 A023426 A023427 this_sequence A023429 A023430 
               A023431
%K A023428 nonn,easy
%O A023428 0,7
%A A023428 Olivier Gerard (olivier.gerard(AT)gmail.com)