A292552 Nontotients of the form 10^k - 2.

98, 998, 9998, 99998, 999998, 9999998, 99999998, 999999998, 9999999998, 99999999998, 999999999998, 9999999999998, 99999999999998, 999999999999998, 9999999999999998, 99999999999999998, 999999999999999998, 9999999999999999998, 99999999999999999998

Offset: 1

Author

Torlach Rush, Sep 18 2017

Keywords

• nonn

Comments

There are no k for which (2^n)*(5^n)[p1*p2*...*pk]-2[p1*p2*...*pk]=m[(p1-1)*(p2-1)*...*(pk-1)].

Up to k = 60, the only totient of the form 10^k-2 is obtained for k=1. - Giovanni Resta, Sep 20 2017

For 10^k-2 with k > 1 to be a totient, it would have to be of the form (p-1)*p^m for some odd prime p and m >= 2. - Robert Israel, Sep 20 2017

Examples

			a(1) = A011557(2) - 2 = A005277(13);
a(2) = A011557(3) - 2 = A005277(210);
a(3) = A011557(4) - 2 = A005277(2627);
a(4) = A011557(5) - 2 = A005277(29747).
		

Crossrefs

Cf. A005277, A011557, A099150.

Extensions

More terms from Giovanni Resta, Sep 20 2017