

A069566


a(1)=0; for n >= 2, a(n) = smallest value of k such that the concatenation 1,n,n^2,..., n^(k1), n^k,n^(k1),...n^2,n,1 is a prime.


1




OFFSET

1,2


COMMENTS

Terms from Robert G. Wilson v.


LINKS

Table of n, a(n) for n=1..6.


EXAMPLE

a(2) = 2 as 12421 is a prime.


MATHEMATICA

Do[k = 0; While[a = Table[n^i, {i, 0, k}]; b = ToExpression[ StringJoin[ ToString /@ Join[a, Drop[ Reverse[a], 1]]]]; !PrimeQ[b], k++ ]; Print[b], {n, 2, 10} ] (* Robert G. Wilson v *)


CROSSREFS

See A239908 for another version.
Sequence in context: A285649 A074956 A176088 * A336314 A066818 A005730
Adjacent sequences: A069563 A069564 A069565 * A069567 A069568 A069569


KEYWORD

more,nonn,base


AUTHOR

Amarnath Murthy, Mar 24 2002


STATUS

approved



