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 A066232 #29 Dec 19 2024 21:16:27
%S A066232 195,3531,9339,27231,46795,78183,90195,112995,135015,437185,849405,
%T A066232 935221,1078581,1283601,1986975,2209585,2341185,2411175,2689695,
%U A066232 2744145,3619071,3712545,4738185,5132985,6596121,7829031,8184715,12176109
%N A066232 Numbers k such that phi(k) = phi(k-2) - phi(k-1).
%C A066232 As in A065557, all terms listed here are odd. Problem: Prove that this holds in general.
%H A066232 Harry J. Smith and Jud McCranie, <a href="/A066232/b066232.txt">Table of n, a(n) for n = 1..289</a> (first 55 terms from Harry J. Smith)
%F A066232 a(n) = A220160(n) + 1 = A197112(n) + 2. - _Andrew Howroyd_, Dec 19 2024
%e A066232 Phi(195) = 96 = 192-96 = phi(193)-phi(194).
%t A066232 Select[Range[3, 10^6], EulerPhi[ # ] == EulerPhi[ # - 2] - EulerPhi[ # - 1] &]
%o A066232 (PARI) isok(k) = { k > 2 && eulerphi(k) == eulerphi(k - 2) - eulerphi(k - 1) } \\ _Harry J. Smith_, Feb 07 2010
%Y A066232 Cf. A065557, A066231, A067701, A197112, A220160.
%K A066232 nonn
%O A066232 1,1
%A A066232 _Joseph L. Pe_, Dec 18 2001
%E A066232 a(13)-a(28) from _Harry J. Smith_, Feb 07 2010