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 A367720 #7 Nov 28 2023 08:39:33
%S A367720 1,1,1,1,1,121,721,2521,6721,196561,3659041,29993041,159762241,
%T A367720 1686639241,60298558321,987112886761,9315623640961,76611297104161,
%U A367720 2454331471018561,69805324167893281,1086439146068753281,62621251106366355481,1358219171406244427281
%N A367720 E.g.f. satisfies A(x) = exp(x*A(x^4)).
%C A367720 This sequence is different from A354554.
%F A367720 a(0) = 1; a(n) = (n-1)! * Sum_{k=0..floor((n-1)/4)} (4*k+1) * a(k) * a(n-1-4*k) / (k! * (n-1-4*k)!).
%o A367720 (PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=(i-1)!*sum(j=0, (i-1)\4, (4*j+1)*v[j+1]*v[i-4*j]/(j!*(i-1-4*j)!))); v;
%Y A367720 Cf. A138292, A367719.
%Y A367720 Cf. A354554.
%K A367720 nonn
%O A367720 0,6
%A A367720 _Seiichi Manyama_, Nov 28 2023