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 A266276 #17 Jan 26 2025 20:53:17
%S A266276 2,3,7,1261,11242771
%N A266276 a(n) is the smallest number k such that phi(k) = n*phi(k-1).
%C A266276 a(n) >= A266269(n). - _Max Alekseyev_, Jan 26 2025
%e A266276 a(3) = 7 because 7 is the smallest number k such that phi(k) = n*phi(k-1); phi(7) = 6 =3*phi(6) = 3*2.
%o A266276 (Magma) a:=func<n|exists(r){k:k in[2..10^8] | EulerPhi(k) eq n*EulerPhi(k-1)}select r else 0>; [a(n):n in[1..5]];
%o A266276 (PARI) a(n) = my(k=2, epk=1, enk); while ((enk=eulerphi(k)) != n*epk, epk = enk; k++); k; \\ _Michel Marcus_, Feb 20 2020
%Y A266276 Sequences of numbers n such that phi(n) = k*phi(n-1): {A001274 + 1} for k=1; A171271 = {A050472 + 1} for k=2; A266268 = {A067143 + 1} for k=3; A268126 = {A172314 + 1} for k=4; {A201253 + 1} for k=5.
%Y A266276 Cf. A000010, A091439, A091456, A266269.
%K A266276 nonn,hard,more
%O A266276 1,1
%A A266276 _Jaroslav Krizek_, Jan 26 2016