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 A353751 #13 May 08 2022 10:34:39 %S A353751 1,2,1,4,1,2,1,8,1,1,1,4,1,2,15,16,1,2,1,4,21,1,1,24,1,2,9,4,1,15,1,8, %T A353751 1,2,1,4,1,2,3,2,1,42,1,4,3,1,1,16,1,2,3,1,1,18,5,8,3,2,1,60,1,2,21, %U A353751 64,1,1,1,4,3,1,1,24,1,2,1,4,7,6,1,16,1,2,1,84,5,2,3,2,1,6,1,4,3,1,5,8,1,2,1,4 %N A353751 a(n) = gcd(n, sigma(sigma(n))), where sigma is the sum of divisors function. %H A353751 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a> %F A353751 a(n) = gcd(n, A051027(n)). %F A353751 a(n) = A051027(n) / A318059(n) = n / A318060(n). %o A353751 (PARI) A353751(n) = gcd(n, sigma(sigma(n))); %Y A353751 Cf. A000203, A051027, A318059, A318060. %Y A353751 Cf. A019278 (positions of fixed points, where a(n)=n). %Y A353751 Cf. also A009194, A295310. %K A353751 nonn %O A353751 1,2 %A A353751 _Antti Karttunen_, May 08 2022