A066152 - OEIS

%I #14 Jun 16 2018 18:37:06

%S 2,459,17835,34089,55419,61183,180785,194139,248501,385671,907323,

%T 988455,1374735,1407413,1408253,1452135,1749087,2451727,3026705,

%U 3263585,3831487,6541695,7633989,9336785,12750833,16543433,16573963,21248201

%N Numbers k such that EulerPhi(k) = sigma(k+1) - sigma(k).

%H Harry J. Smith, <a href="/A066152/b066152.txt">Table of n, a(n) for n = 1..70</a>

%e EulerPhi(459) = 288 = 1008 - 720 = sigma(460) - sigma(459). [corrected by _Harry J. Smith_, Feb 03 2010]

%t Select [Range[1, 10^6], EulerPhi[ # ] == DivisorSigma[1, # + 1] - DivisorSigma[1, # ] & ]

%o (PARI) { n=0; for (m=1, 10^9, if (eulerphi(m) == sigma(m + 1) - sigma(m), write("b066152.txt", n++, " ", m); if (n==70, return)) ) } \\ _Harry J. Smith_, Feb 03 2010

%K nonn

%O 1,1

%A _Joseph L. Pe_, Dec 13 2001

%E More terms from _Robert G. Wilson v_, Dec 27 2001

%E a(25)-a(28) from _Harry J. Smith_, Feb 03 2010