1,1

a(n) is always less than or equal to n-th prime and once past a(6) it is always less than n.

Table of n, a(n) for n=1..103.

a = {}; Do[k = 2; p = Prime[n]; While[ PrimeQ[ FromDigits[ Reverse[ IntegerDigits[p, k]], k]], k++ ]; a = Append[a, k], {n, 1, 105}]; a

Sequence in context: A126607 A124322 A209037 * A239694 A097883 A290020

Adjacent sequences: A075238 A075239 A075240 * A075242 A075243 A075244

base,easy,nonn

Robert G. Wilson v, Sep 09 2002

approved