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%I A066198 #16 Dec 15 2017 17:35:46
%S A066198 2,6,8,10,22,46,58,82,106,166,178,188,226,262,285,346,358,382,466,478,
%T A066198 502,562,586,718,838,854,862,886,902,982,1018,1186,1282,1306,1318,
%U A066198 1366,1438,1486,1522,1618,1822,1906,2013,2026,2038,2062,2098,2206,2446,2458
%N A066198 Numbers n where phi changes as fast as sigma, i.e., abs(phi(n+1) - phi(n)) = abs(sigma(n+1) - sigma(n)).
%C A066198 This sequence is the union of two sequences A145748 and A145749. See comment lines of A145749. [_Farideh Firoozbakht_, Nov 01 2008]
%H A066198 Harry J. Smith, <a href="/A066198/b066198.txt">Table of n, a(n) for n = 1..1000</a>
%e A066198 |phi(7) - phi(6)| = |6 - 2| = |8 - 12| = |sigma(7) - sigma(6)|.
%e A066198 |phi(9) - phi(8)| = |6 - 4| = 2 = |13 - 15| = |sigma(9) - sigma(8)|.
%t A066198 Select[ Range[ 1, 10^4 ], Abs[ DivisorSigma[ 1, # + 1 ] - DivisorSigma[ 1, # ] ] == Abs[ EulerPhi[ # + 1 ] - EulerPhi[ # ] ] & ]
%o A066198 (PARI) { n=0; for (m=1, 10^9, if (abs(eulerphi(m + 1) - eulerphi(m)) == abs(sigma(m + 1) - sigma(m)), write("b066198.txt", n++, " ", m); if (n==1000, return)) ) } \\ _Harry J. Smith_, Feb 05 2010
%Y A066198 Cf. A065387, A145748, A145749.
%K A066198 nonn
%O A066198 1,1
%A A066198 _Joseph L. Pe_, Dec 16 2001
%E A066198 More terms from _Jason Earls_, Jun 05 2002

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