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 A332381 #15 Feb 12 2020 16:18:53
%S A332381 0,0,1,1,0,0,-1,-1,0,0,1,1,2,2,1,1,2,2,3,3,4,4,3,3,2,2,3,3,2,2,1,1,2,
%T A332381 2,1,1,0,0,-1,-1,0,0,1,1,0,0,-1,-1,-2,-2,-1,-1,-2,-2,-3,-3,-2,-2,-3,
%U A332381 -3,-4,-4,-3,-3,-2,-2,-1,-1,-2,-2,-1,-1,0,0,1,1,0
%N A332381 a(n) is the Y-coordinate of the n-th point of the Peano curve. Sequence A332380 gives X-coordinates.
%C A332381 This sequence is the imaginary part of {f(n)} defined as:
%C A332381 - f(0) = 0,
%C A332381 - f(n+1) = f(n) + i^t(n)
%C A332381 where t(n) is the number of 1's and 7's minus the number of 3's and 5's
%C A332381 plus twice the number of 4's in the base 9 representation of n
%C A332381 and i denotes the imaginary unit.
%H A332381 Rémy Sigrist, <a href="/A332381/b332381.txt">Table of n, a(n) for n = 0..6561</a>
%H A332381 <a href="/index/Con#coordinates_2D_curves">Index entries for sequences related to coordinates of 2D curves</a>
%F A332381 a(9^k) = 0 for any k >= 0.
%o A332381 (PARI) { [R,U,L,D]=[0..3]; p = [R,U,R,D,L,D,R,U,R]; z=0; for (n=0, 76, print1 (imag(z) ", "); z += I^vecsum(apply(d -> p[1+d], digits(n, #p)))) }
%Y A332381 Cf. A332380 (X-coordinates and additional comments).
%K A332381 sign,base
%O A332381 0,13
%A A332381 _Rémy Sigrist_, Feb 10 2020