1,1

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

Table of n, a(n) for n=1..19.

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).

Cf. A005277, A011557.

Sequence in context: A202370 A184608 A088736 * A233373 A221747 A190636

Adjacent sequences: A292549 A292550 A292551 * A292553 A292554 A292555

nonn

Torlach Rush, Sep 18 2017

More terms from Giovanni Resta, Sep 20 2017

approved