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 A171369 #11 Jan 04 2019 09:02:02 %S A171369 1,3,3,1,3,3,3,3,1,3,3,3,3,3,3,1,3,3,3,3,3,3,3,3,1,3,3,3,3,3,3,3,3,3, %T A171369 3,1,3,3,3,3,3,3,3,3,3,3,3,3,1,3,3,3,3,3,3,3,3,3,3,3,3,3,3,1,3,3,3,3, %U A171369 3,3,3,3,3,3,3,3,3,3,3,3,1,3,3,3,3,3,3,3,3,3,3 %N A171369 Triangle read by rows, replace 2's with 3's in A169695. %C A171369 Given triangle A275437 (wrapped to contain n terms per row) or sequence A169695, replace 2's with 3's, other terms remain as is. %F A171369 T(n,k) = 1 if n*(n-1)/2+k is a square, otherwise T(n,k) = 3. %e A171369 First few rows of the triangle = %e A171369 . %e A171369 1; %e A171369 3, 3; %e A171369 1, 3, 3; %e A171369 3, 3, 1, 3; %e A171369 3, 3, 3, 3, 3; %e A171369 1, 3, 3, 3, 3, 3; %e A171369 3, 3, 3, 1, 3, 3, 3; %e A171369 3, 3, 3, 3, 3, 3, 3, 1; %e A171369 ... %Y A171369 Cf. A169695, A275437. %K A171369 nonn,easy,tabl %O A171369 1,2 %A A171369 _Gary W. Adamson_, Dec 06 2009 %E A171369 Description corrected by _Robert Israel_, Jan 03 2019