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 A069639 #12 May 08 2025 02:28:16 %S A069639 4,25,121,289,841,1369,2809,4489,6889,10201,16129,22201,29929,38809, %T A069639 51529,66049,85849,109561,134689,160801,196249,237169,292681,332929, %U A069639 398161,458329,537289,619369,727609,822649,935089,1062961,1190281 %N A069639 Smallest composite k such that phi(k) > k*(1-1/n^2). %F A069639 a(n) = nextprime(n^2)^2 = A007918(n^2)^2. %F A069639 a(n) = A007491(n)^2. - _Amiram Eldar_, May 08 2025 %t A069639 a[n_] := NextPrime[n^2]^2; Array[a, 40] (* _Amiram Eldar_, May 08 2025 *) %o A069639 (PARI) a(n) = nextprime(n^2)^2; \\ _Amiram Eldar_, May 08 2025 %Y A069639 Cf. A000010 (phi), A007491, A007918, A069549. %K A069639 easy,nonn %O A069639 1,1 %A A069639 _Benoit Cloitre_, Apr 21 2002