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 A364358 #25 Dec 30 2024 01:52:34
%S A364358 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,1,1,1,1,2,1,1,1,1,
%T A364358 2,1,1,1,1,2,1,1,1,1,2,1,1,1,1,2,1,1,1,1,2,1,1,1,1,2,1,1,1,1,2,1,1,1,
%U A364358 1,2,1,1,1,1,2,1,1,1,1,2,2,1,1,1,2,1,1,1,1,3,1,1,1,1,2,1,1,1,2,2
%N A364358 Number of divisors of n of the form 4*k+1 that are at most sqrt(n).
%H A364358 Robert Israel, <a href="/A364358/b364358.txt">Table of n, a(n) for n = 1..10000</a>
%F A364358 G.f.: Sum_{k>=0} x^(4*k+1)^2 / (1 - x^(4*k+1)).
%p A364358 f:= proc(n) nops(select(t -> t mod 4 = 1 and t^2 <= n, numtheory:-divisors(n))) end proc:
%p A364358 map(f, [$1..100]); # _Robert Israel_, Dec 29 2024
%t A364358 Table[Count[Divisors[n], _?(# <= Sqrt[n] && MemberQ[{1}, Mod[#, 4]] &)], {n, 100}]
%t A364358 nmax = 100; CoefficientList[Series[Sum[x^(4 k + 1)^2/(1 - x^(4 k + 1)), {k, 0, nmax}], {x, 0, nmax}], x] // Rest
%Y A364358 Cf. A001826, A038548, A364387.
%K A364358 nonn
%O A364358 1,25
%A A364358 _Ilya Gutkovskiy_, Jul 21 2023