A092586 - OEIS

%I #10 Mar 17 2015 23:06:44

%S 7,87,231,463,617,691,751,855,1059,1127,2795,4819,11999,18527,22481,

%T 75311,121939,232901,256751,288883,313919,371519,845831,1285841,

%U 1762799,1815167,7195199,9096191,40324121,93070943,99388823,113140151,238072223,487394063

%N Numbers n such that sigma(phi(n))-phi(sigma(n)) is nonzero and is divisible by (n+1), that is A065395(n)/(n+1) = (phi(sigma(n))-sigma(phi(n)))/(n+1) is a nonzero integer.

%e (sigma(phi(x))-phi(sigma(x)))/(x+1) equals 1 if x=7; is 2 if x=463; is 3 if x=4819.

%t f[ x_] := EulerPhi[ DivisorSigma[1, x]] - DivisorSigma[1, EulerPhi[x]]; t = {}; Do[ s = f[n]; If[ s != 0 && Mod[ s, n + 1] == 0, Print[n]; AppendTo[t, n], {n, 2*10^8}]; t

%Y Cf. A033632, A092584-A092588, A000203, A000010, A065395.

%K nonn

%O 1,1

%A _Labos Elemer_, Mar 01 2004

%E Edited and extended by _Robert G. Wilson v_, Mar 03 2004

%E a(33)-a(34) from _Donovan Johnson_, Mar 04 2013