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 A365103 #51 Feb 21 2024 10:47:24
%S A365103 1,2,2,6,18,70,274,1094,4370,17478,69906,279622,1118482,4473926,
%T A365103 17895698,71582790,286331154,1145324614,4581298450,18325193798,
%U A365103 73300775186,293203100742,1172812402962,4691249611846,18764998447378
%N A365103 Number of distinct quartic residues x^4 (mod 4^n), x=0..4^n-1.
%C A365103 a(n) = A364811(2n).
%C A365103 For n>=2, A319281(a(n)) == 4^n + [n mod 2 == 1].
%C A365103 For n>=2, a(n)=k: [ A319281(k) == 4^n + [n mod 2 == 1] ].
%H A365103 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (4, 1, -4).
%F A365103 a(n) = ceiling(4^n/15) + (n mod 2).
%t A365103 a[n_] = Ceiling[4^n/15] + Boole[Mod[n,2]==1]; Array[a, 24]
%o A365103 (PARI) a(n) = ceil(4^n/15)+(Mod(n,2)==1);
%o A365103 (Python)
%o A365103 def A365103(n): return len({pow(x,4,1<<(n<<1)) for x in range(1<<(n<<1))}) # _Chai Wah Wu_, Sep 18 2023
%Y A365103 Cf. A023105, A046631, A195637, A365104, A364811, A319281.
%K A365103 nonn
%O A365103 0,2
%A A365103 _Albert Mukovskiy_, Aug 24 2023