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 A061669 #24 May 03 2022 14:36:15
%S A061669 2,0,0,4,0,12,0,8,9,20,0,12,0,28,30,16,0,18,0,20,42,44,0,24,25,52,27,
%T A061669 28,0,0,0,32,66,68,70,36,0,76,78,40,0,0,0,44,45,92,0,48,49,50,102,52,
%U A061669 0,54,110,56,114,116,0,60,0,124,63,64,130,0,0,68,138,0,0,72,0,148,75
%N A061669 a(n) = n*(mu(n) + 1), where mu(n) is the Moebius function A008683.
%H A061669 Antti Karttunen, <a href="/A061669/b061669.txt">Table of n, a(n) for n = 1..20000</a> (first 1000 terms from Harry J. Smith)
%F A061669 From _Antti Karttunen_, May 03 2022: (Start)
%F A061669 a(n) = n * A007423(n) = n*(1+A008683(n)) = n + A055615(n).
%F A061669 a(1) = 2, and for n > 1, a(n) = -Sum_{d|n, 1<d<n} d * A055615(n/d). [As A000027 and A055615 are Dirichlet inverses of each other]
%F A061669 (End)
%e A061669 a(5) = (5 * -1) + 5 = 0 because mu(5)= -1.
%p A061669 with(numtheory): seq(n*(mobius(n)+1),n=1..80); # _Muniru A Asiru_, Jul 01 2018
%t A061669 Array[# (MoebiusMu[#] + 1) &, 75] (* _Michael De Vlieger_, Jul 01 2018 *)
%o A061669 (PARI) for(n=1,20,print(n*moebius(n)+n))
%o A061669 (PARI) { for (n=1, 1000, write("b061669.txt", n, " ", n*moebius(n) + n) ) } \\ _Harry J. Smith_, Jul 26 2009
%o A061669 (PARI) A061669(n) = (n*(1+moebius(n))); \\ _Antti Karttunen_, May 03 2022
%Y A061669 Cf. A000027, A008683, A007423, A055615.
%Y A061669 Cf. A030059 (positions of 0's), A053850 (positions of odd terms).
%K A061669 easy,nonn
%O A061669 1,1
%A A061669 _Jason Earls_, Jun 16 2001
%E A061669 More terms from _Dean Hickerson_, Jul 24 2001