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%I #2 Mar 30 2012 17:33:59
%S 1,1,2,2,2,3,2,1,2,2,1,1,2,2,3,3,3,3,4,4,3,3,4,5,4,3,2,3,4,4,3,2,1,2,
%T 3,3,3,2,1,1,2,2,3,3,3,4,4,4,4,4,5,5,5,4,4,5,6,6,5,4,4,5,6,7,6,5,4,3,
%U 4,5,6,6,5,4,3,2,3,4,5,5,5,4,3,2,1,2,3,4,4,4,4,3,2,1,1,2,2,3,3,3,4,4,4,4,5
%N Triangle read by rows in which row n contains a finite triangle as shown below.
%e The main triangle begins:
%e 1,
%e 1,2,2,2,3,2,1,2,2,1,
%e 1,2,2,3,3,3,3,4,4,3,3,4,5,4,3,2,3,4,4,3,2,1,2,3,3,3,2,1,
%e 1,2,2,3,3,3,4,4,4,4,4,5,5,5,4,4,5,6,6,5,4,4,5,6,7,6,5,4,3,4,5,6,6,5,4,3,...
%e In which row 1 contains a vertex, only:
%e 1
%e Row 2 contains the triangle:
%e 1
%e 2,2
%e 2,3,2
%e 1,2,2,1
%e Row 3 contains the triangle:
%e 1
%e 2,2
%e 3,3,3
%e 3,4,4,3
%e 3,4,5,4,3
%e 2,3,4,4,3,2
%e 1,2,3,3,3,2,1
%e Row 4 contains the triangle:
%e 1
%e 2,2
%e 3,3,3
%e 4,4,4,4
%e 4,5,5,5,4
%e 4,5,6,6,5,4
%e 4,5,6,7,6,5,4
%e 3,4,5,6,6,5,4,3
%e 2,3,4,5,5,5,4,3,2
%e 1,2,3,4,4,4,4,3,2,1
%e Row 5 contains the triangle:
%e 1
%e 2,2
%e 3,3,3
%e 4,4,4,4
%e 5,5,5,5,5
%e 5,6,6,6,6,5
%e 5,6,7,7,7,6,5
%e 5,6,7,8,8,7,6,5
%e 5,6,7,8,9,8,7,6,5
%e 4,5,6,7,8,8,7,6,5,4
%e 3,4,5,6,7,7,7,6,5,4,3
%e 2,3,4,5,6,6,6,6,5,4,3,2
%e 1,2,3,4,5,5,5,5,5,4,3,2,1
%e And so on...
%K easy,nonn,tabf
%O 1,3
%A _Omar E. Pol_, Nov 09 2009
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