OFFSET
1,2
COMMENTS
FORMULA
a(n) = A000215(n) - 3.
MATHEMATICA
pf[x_] := Part[Reverse[Flatten[FactorInteger[x]]], 2] Do[s=EulerPhi[pf[n]]-pf[EulerPhi[n]]; If[ !Odd[s]&&Greater[s, 2], Print[{n, s}], {n, 3, 10000000}] (* Only 2, 254 and 65534 appear in printout of s. The sequence is provided by Union[{s}, {0, 2}] *)
PROG
(PARI) for(n=0, 4, if(ispseudoprime(t=2^(2^n)+1), print1(t-3", "))) \\ Charles R Greathouse IV, Apr 26 2012
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Labos Elemer, May 09 2002
STATUS
approved