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 A278545 #23 Dec 05 2016 05:00:30 %S A278545 3,5,5,5,8,5,5,8,8,5,5,8,8,8,5,5,8,8,8,8,5,5,8,8,8,8,8,5,5,8,8,8,8,8, %T A278545 8,5,5,8,8,8,8,8,8,8,5,5,8,8,8,8,8,8,8,8,5,5,8,8,8,8,8,8,8,8,8,5,5,8, %U A278545 8,8,8,8,8,8,8,8,8,5,5,8,8,8,8,8,8,8,8,8,8,8,5,5,8,8,8,8,8,8,8,8,8,8,8,8,5 %N A278545 Number of neighbors of the n-th term in a full square array read by antidiagonals. %C A278545 Apart from the first row and the first column, the rest of the elements are 8's. %C A278545 For the same idea but for a right triangle see A278480; for an isosceles triangle see A278481; for a square spiral see A010731; and for a hexagonal spiral see A010722. %H A278545 Robert Israel, <a href="/A278545/b278545.txt">Table of n, a(n) for n = 1..10000</a> %F A278545 G.f. 3+x+8*x/(1-x)-3*(1+x)*Theta_2(0,sqrt(x))/(2*x^(1/8)) where Theta_2 is a Jacobi Theta function. - _Robert Israel_, Dec 04 2016 %e A278545 The corner of the square array begins: %e A278545 3,5,5,5,5,5,5,5,5,5,... %e A278545 5,8,8,8,8,8,8,8,8,... %e A278545 5,8,8,8,8,8,8,8,... %e A278545 5,8,8,8,8,8,8,... %e A278545 5,8,8,8,8,8,... %e A278545 5,8,8,8,8,... %e A278545 5,8,8,8,... %e A278545 5,8,8,... %e A278545 5,8,... %e A278545 5,... %e A278545 ... %p A278545 3, seq(op([5,8$i,5]),i=0..20); # _Robert Israel_, Dec 04 2016 %Y A278545 Antidiagonal sums give 3 together with the elements > 2 of A017089. %Y A278545 Cf. A010722, A010731, A274912, A274913, A278317, A278290, A278480, A278481. %K A278545 nonn,tabl %O A278545 1,1 %A A278545 _Omar E. Pol_, Nov 23 2016