OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..910 (terms below 10^12, calculated from the b-file at A005936; terms 1..100 from Charles R Greathouse IV)
MATHEMATICA
Do[s=Mod[ -1+5^(n-1), n]; If[Equal[s, 0]&&!PrimeQ[n]&&EvenQ[n], Print[n]], {n, 1, 1000000}]
PROG
(PARI) is(n)=Mod(5, n)^(n-1)==1&&!isprime(n)&&n%2==0 \\ Charles R Greathouse IV, Apr 12 2012
(PARI) p=2; forprime(q=3, 1e8, forstep(n=p+1, q-1, 2, if(Mod(5, n)^(n-1)==1, print1(n", "))); p=q) \\ Charles R Greathouse IV, Apr 12 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Nov 25 2003
EXTENSIONS
More terms from Farideh Firoozbakht, Sep 13 2006
STATUS
approved