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 A382477 #39 Apr 17 2025 14:54:39
%S A382477 0,2,3,-4,5,5,7,6,-6,7,11,-1,13,9,8,-8,17,-4,19,1,10,13,23,9,-10,15,9,
%T A382477 3,29,10,31,10,14,19,12,-10,37,21,16,11,41,12,43,7,-1,25,47,-5,-14,-8,
%U A382477 20,9,53,11,16,13,22,31,59,4,61,33,1,-12,18,16,67,13,26,14,71,0,73,39,-7
%N A382477 If n = Product (p_j^k_j) then a(n) = -Sum ((-1)^k_j * k_j * p_j).
%e A382477 a(72) = a(2^3*3^2) = 3*2 - 2*3 = 0.
%t A382477 Join[{0}, Table[-Plus @@ ((-1)^#[[2]] #[[2]] #[[1]] & /@ FactorInteger[n]), {n, 2, 75}]]
%o A382477 (PARI) a(n) = my(f=factor(n)); -sum(k=1, #f~, (-1)^f[k,2]*f[k,2]*f[k,1]); \\ _Michel Marcus_, Apr 17 2025
%Y A382477 Cf. A001414, A008472, A316523, A332422, A332423, A332424, A340901, A366749, A382331.
%K A382477 sign
%O A382477 1,2
%A A382477 _Ilya Gutkovskiy_, Apr 10 2025