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 A131089 #11 Sep 08 2022 08:45:30
%S A131089 1,4,4,6,4,8,4,8,6,8,4,12,4,8,8,10,4,12,4,12,8,8,4,16,6,8,8,12,4,16,4,
%T A131089 12,8,8,8,18,4,8,8,16,4,16,4,12,12,8,4,20,6,12,8,12,4,16,8,16,8,8,4,
%U A131089 24,4,8,12,14,8,16,4,12,8,16,4,24,4,8,12,12,8,16
%N A131089 a(n) = Sum_{d|n} (2 - mu(d)).
%C A131089 Apart from the first term the same as A062011. - _Andrew Howroyd_, Aug 09 2018
%F A131089 a(n) = 2*tau(n) = A062011(n) for n > 1. - _Andrew Howroyd_, Aug 09 2018
%F A131089 Inverse Moebius transform of A228483.
%e A131089 a(4) = 6 = (2 + 3 + 0 + 1), row 4 of A131088.
%t A131089 Join[{1}, Table[2 DivisorSigma[0, n], {n, 100}]] (* _Vincenzo Librandi_, Aug 10 2018 *)
%o A131089 (PARI) a(n)={2*numdiv(n) - (n==1)} \\ _Andrew Howroyd_, Aug 09 2018
%o A131089 (Magma) [1] cat [2*NumberOfDivisors(n) : n in [2..100] ]; // _Vincenzo Librandi_, Aug 10 2018
%Y A131089 Row sums of triangle A131088.
%Y A131089 Cf. A062011, A051731, A131090, A228483.
%K A131089 nonn
%O A131089 1,2
%A A131089 _Gary W. Adamson_, Jun 14 2007
%E A131089 Name changed and terms a(10) and beyond from _Andrew Howroyd_, Aug 09 2018