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%I #25 Feb 11 2014 19:05:23
%S 195,3531,9339,27231,46795,78183,90195,112995,135015,437185,849405,
%T 935221,1078581,1283601,1986975,2209585,2341185,2411175,2689695,
%U 2744145,3619071,3712545,4738185,5132985,6596121,7829031,8184715,12176109
%N Numbers n such that phi(n) = phi(n-2) - phi(n-1).
%C As in A065557, all terms listed here are odd. Problem: Prove that this holds in general.
%H 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)
%e Phi(195) = 96 = 192-96 = phi(193)-phi(194).
%t Select[Range[3, 10^6], EulerPhi[ # ] == EulerPhi[ # - 2] - EulerPhi[ # - 1] &]
%o (PARI) { n=0; for (m=3, 10^9, if (eulerphi(m) == eulerphi(m - 2) - eulerphi(m - 1), write("b066232.txt", n++, " ", m); if (n==100, return)) ) } \\ _Harry J. Smith_, Feb 07 2010
%Y Cf. A066231, A067701.
%K nonn
%O 1,1
%A _Joseph L. Pe_, Dec 18 2001
%E a(13)-a(28) from _Harry J. Smith_, Feb 07 2010
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