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 A370837 #9 Mar 03 2024 09:53:04
%S A370837 1,1,1,0,-3,-9,-15,-6,57,231,501,474,-1223,-7331,-19655,-27813,19089,
%T A370837 248541,819141,1508316,417165,-8314449,-34737603,-78646452,-71651147,
%U A370837 251348311,1461221581,3984339966,5586567405,-5424531663,-59608307151,-196443394947
%N A370837 Expansion of (1/x) * Series_Reversion( x/(x+1/(1+x^3)) ).
%H A370837 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A370837 a(n) = Sum_{k=0..floor(n/3)} (-1)^k * binomial(n,3*k) * binomial(4*k,k)/(3*k+1).
%o A370837 (PARI) my(N=40, x='x+O('x^N)); Vec(serreverse(x/(x+1/(1+x^3)))/x)
%o A370837 (PARI) a(n) = sum(k=0, n\3, (-1)^k*binomial(n, 3*k)*binomial(4*k, k)/(3*k+1));
%Y A370837 Cf. A370836, A370838.
%Y A370837 Cf. A226974, A370800.
%K A370837 sign
%O A370837 0,5
%A A370837 _Seiichi Manyama_, Mar 03 2024