A066820 - OEIS

%I #11 Dec 25 2015 00:23:34

%S 1,2,4,6,6,10,14,16,20,24,26,25,36,40,48,54,56,60,66,74,84,90,94,110,

%T 116,120,124,126,98,130,134,146,150,156,160,170,176,180,184,150,204,

%U 206,210,192,224,230,236,240,250,256,260,264,270,280,284,300,306,314,326

%N Integers of the form phi(n^2+1)/n.

%C If k^2 + 1 is prime, phi(k^2 + 1)/k = k, hence A005574(n) is included in the sequence. For odd values see A066852.

%H Harry J. Smith, <a href="/A066820/b066820.txt">Table of n, a(n) for n = 1..1000</a>

%o (PARI) { n=0; for (m=1, 10^10, if (eulerphi(m^2 + 1) % m == 0, write("b066820.txt", n++, " ", eulerphi(m^2 + 1) / m); if (n==1000, return)) ) } \\ _Harry J. Smith_, Mar 29 2010

%Y Cf. A066852.

%K nonn

%O 1,2

%A _Benoit Cloitre_, Jan 19 2002

%E Term n=51 a=260 added by _Harry J. Smith_, Mar 29 2010