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 A080818 #5 Mar 12 2015 20:04:56 %S A080818 1,1,3,1,2,6,1,2,3,10,1,2,3,4,6,1,2,3,4,5,10,1,2,3,4,5,6,15,1,2,3,4,5, %T A080818 6,7,8,1,2,3,4,5,6,7,8,13,1,2,3,4,5,6,7,8,9,19,1,2,3,4,5,6,7,8,9,10, %U A080818 26,1,2,3,4,5,6,7,8,9,10,11,15,1,2,3,4,5,6,7,8,9,10,11,12,22,1,2,3,4,5,6,7,8 %N A080818 Triangle read by rows in which the n-th row contains n distinct numbers whose sum is the smallest square. %C A080818 If n(n+1)/2 is a square triangular number then the n-th row contains first n natural numbers (e.g., the 8th row). %e A080818 1; 1,3; 1,2,6; 1,2,3,10; 1,2,3,4,6; 1,2,3,4,5,10; 1,2,3,4,5,6,15; 1,2,3,4,5,6,... %p A080818 seq(op([seq(i,i=1..n-1),(ceil(sqrt(n*(n+1)/2)))^2 - n*(n-1)/2]),n=1..15); # C. Ronaldo %Y A080818 Cf. A080817, A080819, A080820. %K A080818 nonn,tabl %O A080818 1,3 %A A080818 _Amarnath Murthy_, Mar 21 2003 %E A080818 More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 19 2004