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 A367692 #12 Nov 30 2023 16:10:35 %S A367692 1,2,3,4,5,8,13,20,29,43,66,102,155,233,352,536,817,1240,1878,2848, %T A367692 4327,6576,9984,15150,22995,34919,53029,80513,122224,185556,281736, %U A367692 427776,649481,986054,1497069,2272976,3451038,5239607,7955067,12077876,18337503 %N A367692 G.f. A(x) satisfies A(x) = 1 / ((1 - x) * (1 - x * A(x^4))). %F A367692 a(n) = 1 + Sum_{k=0..floor((n-1)/4)} a(k) * a(n-1-4*k). %o A367692 (PARI) a_vector(n) = my(v=vector(n+1)); for(i=0, n, v[i+1]=1+sum(j=0, (i-1)\4, v[j+1]*v[i-4*j])); v; %o A367692 (Python) %o A367692 from functools import lru_cache %o A367692 @lru_cache(maxsize=None) %o A367692 def A367692(n): return 1+sum(A367692(k)*A367692(n-1-(k<<2)) for k in range(n+3>>2)) # _Chai Wah Wu_, Nov 30 2023 %Y A367692 Cf. A007317, A351972, A367691. %Y A367692 Cf. A367660. %K A367692 nonn %O A367692 0,2 %A A367692 _Seiichi Manyama_, Nov 27 2023