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 A073351 #5 Sep 24 2021 11:57:29 %S A073351 0,4,125,1078,5220,18150,50869,122500,263568,519840,956725,1664234, %T A073351 2762500,4407858,6799485,10186600,14876224,21241500,29730573,40876030, %U A073351 55304900,73749214,97057125,126204588,162307600,206635000,260621829 %N A073351 n^2(n+1)(2n+1)^2(7n+1)/36. %D A073351 Mentioned in a problem on p. 334 of Two-Year College Math. Jnl., Vol. 25, 1994. %H A073351 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (7,-21,35,-35,21,-7,1). %F A073351 a(n)=sum(i=1, n, i^2)*sum(i=n+1, 2*n, i^2). %F A073351 G.f.: x(4+97x+287x^2+159x^3+13x^4)/(1-x)^7. %Y A073351 Cf. A007750. %K A073351 nonn,easy %O A073351 0,2 %A A073351 _Michael Somos_, Jul 27 2002