This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A278480 #12 Nov 23 2016 11:30:17 %S A278480 2,4,5,5,7,5,5,8,7,5,5,8,8,7,5,5,8,8,8,7,5,5,8,8,8,8,7,5,5,8,8,8,8,8, %T A278480 7,5,5,8,8,8,8,8,8,7,5,5,8,8,8,8,8,8,8,7,5,5,8,8,8,8,8,8,8,8,7,5,5,8, %U A278480 8,8,8,8,8,8,8,8,7,5,5,8,8,8,8,8,8,8,8,8,8,7,5,5,8,8,8,8,8,8,8,8,8,8,8,7,5 %N A278480 Number of neighbors of the n-th term in a full right triangle read by rows. %C A278480 Apart from the first column and the first two diagonals, the rest of the elements are 8's. %C A278480 For the same idea but for an isosceles triangle see A278481; for a square array see A278545, for a square spiral see A010731; and for a hexagonal spiral see A010722. %e A278480 The sequence written as a right triangle begins: %e A278480 2; %e A278480 4, 5; %e A278480 5, 7, 5; %e A278480 5, 8, 7, 5; %e A278480 5, 8, 8, 7, 5; %e A278480 5, 8, 8, 8, 7, 5; %e A278480 5, 8, 8, 8, 8, 7, 5; %e A278480 5, 8, 8, 8, 8, 8, 7, 5; %e A278480 5, 8, 8, 8, 8, 8, 8, 7, 5; %e A278480 5, 8, 8, 8, 8, 8, 8, 8, 7, 5; %e A278480 ... %Y A278480 Row sums give 2 together with the elements > 1 of A017077. %Y A278480 Also, row sums give 2 together with A004768. %Y A278480 Cf. A010722, A010731, A278317, A278481, A278545. %K A278480 nonn,tabl %O A278480 1,1 %A A278480 _Omar E. Pol_, Nov 23 2016