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 A367866 #19 Dec 06 2023 08:34:04
%S A367866 1,7,13,7,31,91,57,7,13,217,133,91,183,399,403,7,307,91,381,217,741,
%T A367866 931,553,91,31,1281,13,399,871,2821,993,7,1729,2149,1767,91,1407,2667,
%U A367866 2379,217,1723,5187,1893,931,403,3871,2257,91,57,217,3991,1281,2863,91
%N A367866 a(n) = Sum_{d|n} d * sigma(d) * mu(d)^2.
%C A367866 Inverse Möbius transform of n * sigma(n) * mu(n)^2.
%H A367866 N. J. A. Sloane, <a href="/transforms.txt">Transforms</a>.
%F A367866 Multiplicative with a(p^e) = p^2 + p + 1. - _Amiram Eldar_, Dec 04 2023
%F A367866 Sum_{k=1..n} a(k) ~ n^3/3. - _Vaclav Kotesovec_, Dec 05 2023
%t A367866 Table[Sum[d*DivisorSigma[1, d]*MoebiusMu[d]^2, {d, Divisors[n]}], {n, 100}]
%o A367866 (PARI) a(n) = sumdiv(n, d, if (issquarefree(d), d*sigma(d))); \\ _Michel Marcus_, Dec 04 2023
%o A367866 (Python)
%o A367866 from math import prod
%o A367866 from sympy import primefactors
%o A367866 def A367866(n): return prod(p*(p+1)+1 for p in primefactors(n)) # _Chai Wah Wu_, Dec 05 2023
%Y A367866 Cf. A000203 (sigma), A008966 (mu^2), A343442.
%K A367866 nonn,easy,mult
%O A367866 1,2
%A A367866 _Wesley Ivan Hurt_, Dec 03 2023