OFFSET
1,2
COMMENTS
a(7) > 5*10^11. - Giovanni Resta, Sep 23 2017
EXAMPLE
10393 = 19*547 is a term because 2^((19 + 1)*(547 + 1)) == (19 - 1)*(547 - 1) (mod 19*547).
PROG
(PARI) a001615(n) = my(f=factor(n)); prod(i=1, #f~, f[i, 1]^f[i, 2] + f[i, 1]^(f[i, 2]-1));
isok(n) = n%2==1 && Mod(2, n)^a001615(n)==eulerphi(n); \\ after Charles R Greathouse IV at A001615
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Altug Alkan, Sep 22 2017
EXTENSIONS
a(5)-a(6) from Giovanni Resta, Sep 23 2017
STATUS
approved