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 A134156 #15 Feb 17 2024 14:51:56
%S A134156 1,2,1,2,-1,2,-3,0,-3,-2,-7,0,-9,-6,-7,-6,-13,-6,-15,-8,-13,-14,-19,
%T A134156 -8,-19,-18,-19,-16,-25,-14,-27,-20,-25,-26,-27,-18,-33,-30,-31,-24,
%U A134156 -37,-26,-39,-32,-33,-38,-43,-28,-43,-38,-43,-40,-49,-38,-47,-40,-49,-50,-55,-36
%N A134156 a(n) = 2*tau(n) - n, where tau(n) is the number of divisors of n (A000005).
%H A134156 Andrew Howroyd, <a href="/A134156/b134156.txt">Table of n, a(n) for n = 1..1000</a>
%F A134156 a(n) = A000005(n) - A049820(n).
%F A134156 a(n) = n - 2*A049820(n). - _Wesley Ivan Hurt_, Feb 17 2024
%o A134156 (PARI) a(n) = {2*numdiv(n) - n} \\ _Andrew Howroyd_, Feb 02 2020
%Y A134156 Cf. A000005 (tau), A049820.
%K A134156 sign,easy
%O A134156 1,2
%A A134156 _Paul Curtz_, Jan 12 2008
%E A134156 Offset corrected and terms a(21) and beyond from _Andrew Howroyd_, Feb 02 2020