Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #30 Nov 23 2016 11:29:44
%S 0,1,2,2,3,2,2,4,3,2,2,4,4,3,2,2,4,4,4,3,2,2,4,4,4,4,3,2,2,4,4,4,4,4,
%T 3,2,2,4,4,4,4,4,4,3,2,2,4,4,4,4,4,4,4,3,2,2,4,4,4,4,4,4,4,4,3,2,2,4,
%U 4,4,4,4,4,4,4,4,3,2,2,4,4,4,4,4,4,4,4,4,4,3,2,2,4,4,4,4,4,4,4,4,4,4,4,3,2
%N Number of neighbors of each new term in a right triangle read by rows.
%C To evaluate T(n,k) consider only the neighbors of T(n,k) that are present in the triangle when T(n,k) should be a new term in the triangle.
%C Apart from the first column and the first two diagonals the rest of the elements are 4's.
%C For the same idea but for an isosceles triangle see A275015; for a square array see A278290, for a square spiral see A278354; and for a hexagonal spiral see A047931.
%e Triangle begins:
%e 0;
%e 1, 2;
%e 2, 3, 2;
%e 2, 4, 3, 2;
%e 2, 4, 4, 3, 2;
%e 2, 4, 4, 4, 3, 2;
%e 2, 4, 4, 4, 4, 3, 2;
%e 2, 4, 4, 4, 4, 4, 3, 2;
%e 2, 4, 4, 4, 4, 4, 4, 3, 2;
%e 2, 4, 4, 4, 4, 4, 4, 4, 3, 2;
%e ...
%Y Apart from the initial zero, row sums give A004767.
%Y Column 1 is A130130.
%Y Columns > 1 give the terms greater than 1 of A158411.
%Y Right border gives 0 together with A007395, also twice A057427.
%Y Second right border gives A122553.
%Y Cf. A047931, A274912, A274913, A275015, A278290, A278317, A278354,
%K nonn,tabl
%O 1,3
%A _Omar E. Pol_, Nov 18 2016