|
%I #7 Jun 16 2015 14:20:19
%S 0,0,3,3,5,4,5,5,4,4,6,7,7,7,7,4,8,8,9,6,9,9,11,7,7,9,11,11,13,10,13,
%T 10,12,11,13,17,14,11,12,9,16,9,6,13,15,10,6,11,19,12,19,13,11,16,7,
%U 17,19,19,12,7,16,19,7,10,13,19,22,7,19,19,18,18,21,10
%N Least base b >= 2 such that prime(n) is an absolute prime in base b with at least 2 distinct digits or 0 if no such base exists.
%C a(n) < prime(n)-1. This is true since prime(n) in base b > prime(n) has a single digit, prime(n) in base prime(n) is written as 10 which is not an absolute prime and prime(n) in base prime(n)-1 is written as 11 which does not have 2 distinct digits.
%C For 1 <= n <= 10000, A258778 differs from A258802 for 50 values of n.
%C Conjecture: a(n) = 0 if and only if n=1 or n=2.
%H Chai Wah Wu, <a href="/A258802/b258802.txt">Table of n, a(n) for n = 1..10000</a>
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Permutable_prime">Permutable prime</a>
%e See example in A258778.
%Y Cf. A003459, A258706, A258778.
%K nonn
%O 1,3
%A _Chai Wah Wu_, Jun 11 2015
|
