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 A075853 #9 Jul 02 2025 19:28:28
%S A075853 1,1,1,2,3,6,13,27,59,131,295,684,1609,3829,9203,22262,54179,132565,
%T A075853 325823,804108,1991729,4949794,12339483,30851429,77347913,194422788,
%U A075853 489892473,1237207811,3131186993,7940340037,20173254851,51341234278
%N A075853 G.f. satisfies A(x) = 1 + x (1+Sum_{n=0..inf} [xA(x)]^(2^n)).
%o A075853 (PARI) a(n)=local(A,m); if(n<3,n>=0,A=1+x*O(x^n); m=1+ceil(log(n)/log(2)); for(k=1,n,A*=x; A=1+x*sum(i=0,m,A^2^i,1)); polcoeff(A,n))
%K A075853 nonn
%O A075853 0,4
%A A075853 _Paul D. Hanna_, Oct 15 2002
%E A075853 Definition corrected by _Michael Somos_, Oct 29 2002