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 A383526 #7 Apr 29 2025 08:54:52
%S A383526 1,1,1,4,17,46,112,365,1297,4126,12686,41647,141440,470887,1553021,
%T A383526 5205769,17665105,59858038,202599814,689183087,2355887902,8065291637,
%U A383526 27637715887,94924591313,326810899744,1126888746871,3890420726167,13450563963085,46571447873597
%N A383526 a(n) = Sum_{k=0..floor(n/3)} binomial(n,k) * binomial(n-2*k,k)^2.
%C A383526 Diagonal of the rational function 1 / ((1-x)*(1-y)*(1-z) - x*y^3*z^3).
%o A383526 (PARI) a(n) = sum(k=0, n\3, binomial(n, k)*binomial(n-2*k, k)^2);
%Y A383526 Cf. A000172, A248658, A383525.
%K A383526 nonn
%O A383526 0,4
%A A383526 _Seiichi Manyama_, Apr 29 2025