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 A353640 #11 May 05 2022 11:06:06
%S A353640 0,1,1,1,2,3,1,3,0,3,1,1,2,1,3,1,0,3,3,3,2,3,3,1,0,1,1,1,2,3,1,1,2,1,
%T A353640 1,3,0,3,3,3,2,1,3,1,0,1,3,3,2,3,1,3,0,1,1,1,2,1,1,3,2,3,1,3,0,1,1,1,
%U A353640 2,1,1,3,0,3,3,3,2,1,3,1,0,1,3,3,2,3,1,3,0,1,3,1,0,1,3,3,2,3,1,3,0,1,1,1,2,1
%N A353640 Čiurlionis sequence A342002, reduced modulo 4.
%H A353640 Antti Karttunen, <a href="/A353640/b353640.txt">Table of n, a(n) for n = 0..65537</a>
%H A353640 <a href="/index/Pri#primorialbase">Index entries for sequences related to primorial base</a>
%F A353640 a(n) = A010873(A342002(n)).
%F A353640 a(n) = A010873(A328572(n)*A353630(n)). [Note that all terms of A328572 are odd]
%o A353640 (PARI) A353640(n) = { my(s=0, m=1, p=2, e); while(n, e = (n%p); m *= p^(e>0); s += (e/p); n = n\p; p = nextprime(1+p)); ((s*m)%4); };
%Y A353640 Cf. A010873, A166486 (parity of terms), A342002, A353630.
%Y A353640 Cf. A353641, A353642 (bisections).
%K A353640 nonn,base
%O A353640 0,5
%A A353640 _Antti Karttunen_, May 01 2022