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 A371743 #10 Apr 05 2024 13:06:33 %S A371743 1,4,29,231,1926,16491,143683,1267395,11282393,101151544,912011633, %T A371743 8260998772,75115815749,685232639419,6268299350776,57478389714473, %U A371743 528167137069958,4862304525663579,44836026545219765,414048025058547788,3828677665694353049 %N A371743 a(n) = Sum_{k=0..floor(n/2)} binomial(4*n-k,n-2*k). %F A371743 a(n) = [x^n] 1/((1-x-x^2) * (1-x)^(3*n)). %F A371743 a(n) ~ 2^(8*n + 5/2) / (11 * sqrt(Pi*n) * 3^(3*n - 1/2)). - _Vaclav Kotesovec_, Apr 05 2024 %o A371743 (PARI) a(n) = sum(k=0, n\2, binomial(4*n-k, n-2*k)); %Y A371743 Cf. A108081, A371742, A371744. %K A371743 nonn %O A371743 0,2 %A A371743 _Seiichi Manyama_, Apr 05 2024