A281909 - OEIS

%I #19 Mar 06 2017 12:27:29

%S 2,3,7,7,25,25,49,49,49,49,49,49,81,81,81,81,241,241,289,289,289,289,

%T 289,289,289,289,289,289,289,289,721,721,721,721,721,721,961,961,961,

%U 961,961,961

%N Smallest k such that k^i - 1 is a totient number (A002202) for all i = 1 to n, or 0 if no such k exists.

%e a(3) = 7 because 7 - 1 = 6, 7^2 - 1 = 48, 7^3 - 1 = 342 are all totient numbers and 7 is the least number with this property.

%Y Cf. A000010, A002202, A045542.

%K nonn,more

%O 1,1

%A _Altug Alkan_, Feb 01 2017

%E a(18)-a(42) from _Max Alekseyev_, Feb 07 2017, Mar 06 2017