A292742 Odd numbers k such that 2^psi(k) == phi(k) (mod k).

1, 5, 10393, 45411263, 31761301667, 70697569679

Offset: 1

Author

Altug Alkan, Sep 22 2017

Keywords

• nonn
• more

Comments

a(7) > 5*10^11. - Giovanni Resta, Sep 23 2017

Examples

			10393 = 19*547 is a term because 2^((19 + 1)*(547 + 1)) == (19 - 1)*(547 - 1) (mod 19*547).
		

Crossrefs

Cf. A000010, A001615, A292544.

Programs

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

Extensions

a(5)-a(6) from Giovanni Resta, Sep 23 2017