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%I #17 Nov 23 2016 11:30:24
%S 2,4,4,4,6,4,4,6,6,4,4,6,6,6,4,4,6,6,6,6,4,4,6,6,6,6,6,4,4,6,6,6,6,6,
%T 6,4,4,6,6,6,6,6,6,6,4,4,6,6,6,6,6,6,6,6,4,4,6,6,6,6,6,6,6,6,6,4,4,6,
%U 6,6,6,6,6,6,6,6,6,4,4,6,6,6,6,6,6,6,6,6,6,6,4
%N Number of neighbors of the n-th term in a full isosceles triangle read by rows.
%C Apart from the left border and the right border, the rest of the elements are 6's.
%C For the same idea but for a right triangle see A278480; for a square array see A278545, for a square spiral see A010731; and for a hexagonal spiral see A010722.
%e The sequence written as an isosceles triangle begins:
%e .
%e . 2;
%e . 4, 4;
%e . 4, 6, 4;
%e . 4, 6, 6, 4;
%e . 4, 6, 6, 6, 4;
%e . 4, 6, 6, 6, 6, 4;
%e . 4, 6, 6, 6, 6, 6, 4;
%e . 4, 6, 6, 6, 6, 6, 6, 4;
%e . 4, 6, 6, 6, 6, 6, 6, 6, 4;
%e . 4, 6, 6, 6, 6, 6, 6, 6, 6, 4;
%e ...
%Y Row sums give A016933.
%Y Left border gives A040002, the same as the right border.
%Y Middle column gives the elements > 1 of A134201, also twice A122553.
%Y Cf. A010722, A010731, A275015, A278317, A278480, A278545.
%K nonn,tabl
%O 1,1
%A _Omar E. Pol_, Nov 23 2016
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