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 A057057 #10 Jul 09 2025 03:55:26
%S A057057 1,3,4,6,8,11,13,15,18,21,24,27,30,33,37,40,44,48,52,55,60,64,68,72,
%T A057057 76,81,85,90,95,100,104,109,114,119,125,130,135,141,146,152,157,163,
%U A057057 168,174,180,186,192,198,204,210,216,223,229
%N A057057 Let R(i,j) be the rectangle with antidiagonals 1; 2,3; 4,5,6; ...; C(n,3) is in antidiagonal a(n).
%F A057057 Round(sqrt(2*binomial(n, 3))). - _Vladeta Jovovic_, Jun 14 2003
%t A057057 Table[Round[Sqrt[2*Binomial[n,3]]],{n,3,60}] (* _Harvey P. Dale_, Nov 16 2021 *)
%Y A057057 Cf. A057045, A057062, A057048, A022846, A057054.
%K A057057 nonn
%O A057057 3,2
%A A057057 _Clark Kimberling_, Jul 30 2000