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 A378930 #28 Dec 17 2024 19:51:58 %S A378930 1,1,6,12,10,6,14,2,3,10,22,2,26,14,60,80,34,3,38,30,84,22,46,3,75,26, %T A378930 108,42,58,60,62,48,132,34,140,4,74,38,156,5,82,84,86,66,30,46,94,120, %U A378930 147,75,204,78,106,108,220,7,228,58,118,5,122,62,42,448,260 %N A378930 a(n) = n * d(n) / gcd(n, d(n))^2, where d = A000005. %H A378930 Viliam Furík, <a href="/A378930/b378930.txt">Table of n, a(n) for n = 1..10000</a> %F A378930 a(n) = A038040(n)/A009191(n)^2. %F A378930 a(n) = A009230(n)/A009191(n). %p A378930 a:= n-> (d-> n*d/igcd(n,d)^2)(numtheory[tau](n)): %p A378930 seq(a(n), n=1..65); # _Alois P. Heinz_, Dec 11 2024 %t A378930 a[n_]:= n * DivisorSigma[0,n]/GCD[n, DivisorSigma[0,n]]^2; Array[a,65] (* _Stefano Spezia_, Dec 11 2024 *) %o A378930 (PARI) a(n) = my(d = numdiv(n)); n * d / gcd(n, d)^2; \\ _Amiram Eldar_, Dec 11 2024 %Y A378930 Cf. A000005, A009191, A009230, A038040. %K A378930 nonn %O A378930 1,3 %A A378930 _Viliam Furík_, Dec 11 2024