login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A069566 a(1)=0; for n >= 2, a(n) = smallest value of k such that the concatenation 1,n,n^2,..., n^(k-1), n^k,n^(k-1),...n^2,n,1 is a prime. 1
0, 2, 1, 12, 1, 2 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 18 04:58 EDT 2021. Contains 343994 sequences. (Running on oeis4.)