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 A357260 #14 Sep 21 2022 12:02:09
%S A357260 1,2,3,4,5,8,7,9,9,14,11,16,13,20,18,19,17,28,19,26,26,32,23,36,25,38,
%T A357260 31,38,29,54,31,41,42,50,38,56,37,56,50,56,41,76,43,62,58,68,47,78,49,
%U A357260 78,66,74,53,92,62,76,74,86,59,114,61,92,78,85,74,124,67,98,90,118
%N A357260 a(n) is the number of 2 X 2 Euclid-reduced matrices having coprime elements and determinant n.
%C A357260 See Bacher link for the definition of Euclid-reduced.
%H A357260 Roland Bacher, <a href="https://arxiv.org/abs/2209.09529">Euclid meets Popeye: The Euclidean Algorithm for 2X2 matrices</a>, arXiv:2209.09529 [math.NT], 2022.
%F A357260 a(n) = Sum_{d^2|n} moebius(d)*A357259(n/d^2).
%t A357260 f[n_] := DivisorSum[n, # + 1 - n/# &, #^2 >= n &]; a[n_] := DivisorSum[n, MoebiusMu[Sqrt[#]] * f[n/#] &, IntegerQ[Sqrt[#]] &]; Array[a, 100] (* _Amiram Eldar_, Sep 21 2022 *)
%o A357260 (PARI) f(n) = sumdiv(n, d, if (d^2 >= n, d + 1 -n/d)); \\ A357259
%o A357260 a(n) = sumdiv(n, d, if (issquare(d), moebius(sqrtint(d))*f(n/d)));
%Y A357260 Cf. A357259.
%K A357260 nonn
%O A357260 1,2
%A A357260 _Michel Marcus_, Sep 21 2022