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 A069549 #14 May 08 2025 02:28:36 %S A069549 4,4,9,25,25,49,49,121,121,121,121,169,169,289,289,289,289,361,361, %T A069549 529,529,529,529,841,841,841,841,841,841,961,961,1369,1369,1369,1369, %U A069549 1369,1369,1681,1681,1681,1681,1849,1849,2209,2209,2209,2209,2809,2809,2809 %N A069549 Smallest composite k such that phi(k) > k*(1-1/n). %C A069549 Or, least composite k such that k is coprime to the n-1 numbers k+1 ... k+n-1. E.g., a(4) = 25 because 25 is coprime to 26, 27 and 28. - _Amarnath Murthy_, Apr 20 2004 %F A069549 a(n) = nextprime(n)^2 = A007918(n)^2. %t A069549 a[n_] := NextPrime[n-1]^2; Array[a, 50] (* _Amiram Eldar_, May 08 2025 *) %o A069549 (PARI) a(n) = nextprime(n)^2; \\ _Amiram Eldar_, May 08 2025 %Y A069549 Cf. A000010 (phi), A007918, A052349. %K A069549 easy,nonn %O A069549 1,1 %A A069549 _Benoit Cloitre_, Apr 21 2002 %E A069549 Edited by _David Wasserman_, Apr 23 2007