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%I #15 Jun 29 2017 11:46:43
%S 1,2,2,2,3,2,2,3,3,2,2,3,3,3,2,2,3,3,3,3,2,2,3,3,3,3,3,2,2,3,3,3,3,3,
%T 3,2,2,3,3,3,3,3,3,3,2,2,3,3,3,3,3,3,3,3,2,2,3,3,3,3,3,3,3,3,3,2,2,3,
%U 3,3,3,3,3,3,3,3,3,2,2,3,3,3,3,3,3,3,3,3,3,3,2,2,3,3,3,3,3,3,3,3,3,3,3,3,2
%N One half of A278481.
%C Apart from the left border and the right border, the rest of the elements are 3's.
%F a(n) = A278481(n)/2.
%e The sequence written as a triangle begins:
%e 1;
%e 2, 2;
%e 2, 3, 2;
%e 2, 3, 3, 2;
%e 2, 3, 3, 3, 2;
%e 2, 3, 3, 3, 3, 2;
%e 2, 3, 3, 3, 3, 3, 2;
%e 2, 3, 3, 3, 3, 3, 3, 2;
%e 2, 3, 3, 3, 3, 3, 3, 3, 2;
%e 2, 3, 3, 3, 3, 3, 3, 3, 3, 2;
%e ...
%Y Row sums give A016777.
%Y Left border gives A040000, the same as the right border.
%Y Middle column gives A122553.
%Y Every diagonal that is parallel to any of the borders gives the elements greater than 1 of A158799.
%Y Cf. A278481.
%K nonn,tabl
%O 1,2
%A _Omar E. Pol_, Nov 23 2016
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