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 A249752 #61 Jul 06 2016 23:48:54 %S A249752 1,1,2,3,5,6,14,52,60,47 %N A249752 Triangle read by rows: T(n,k) = number of arrangements of n circles in the affine plane having k outer circles. %C A249752 Consider the arrangements of n circles described in A250001. %C A249752 T(n,k) is the number of arrangements of n circles in the affine plane whose perimeters are formed with parts from k circles. - _Omar E. Pol_, Aug 09 2015 %C A249752 From _Omar E. Pol_, Jul 06 2016: (Start) %C A249752 Observation 1: column 1 gives A250001, at least if 1<=n<=4. %C A249752 Observation 2: sum of n-th row = T(n+1,1), at least if 1<=n<=3. (End) %e A249752 Triangle begins: %e A249752 1; %e A249752 1, 2; %e A249752 3, 5, 6; %e A249752 14, 52, 60, 47; %e A249752 ... %Y A249752 Sum of n-th row = A250001(n). %Y A249752 Leading diagonal gives A274702. %Y A249752 Cf. A252158, A261070, A274776, A274777. %K A249752 nonn,tabl,hard,more %O A249752 1,3 %A A249752 _Omar E. Pol_, Dec 14 2014 %E A249752 Corrected a(5)-a(6) and added a(7)-a(10) from _Omar E. Pol_, Oct 13 2015