A068008 Least number needed to be appended to n n's to make a prime that does not contain more than n n's in a row.

2, 3, 3, 1, 9, 7, 29, 39, 3, 43, 39, 1, 23, 27, 97, 53, 91, 37, 251, 93, 93, 19, 97, 61, 293, 153, 163, 1, 297, 103, 323, 61, 127, 113, 31, 127, 353, 67, 841, 187, 9, 21, 179, 429, 127, 97, 3, 319, 11, 51, 39, 191, 33, 3, 41, 151, 39, 47, 169, 787, 401, 57, 441, 571

Offset

0,1

Comments

This is not quite the "tail" of the numbers in A068120 because of the restriction that a(n) cannot begin with a zero. For example, a(25) = 153; 25252525252525252525252525252525252525252525252525153 is a prime, but it is greater than A068120(25) = 25252525252525252525252525252525252525252525252525061. - Dan Dima, Jan 29 2007

Links

Table of n, a(n) for n=0..63.

Example

a(0) = 2 because appending 2 to a zero-length string (i.e., 0 0's) yields 2, which is prime.
a(1) = 3 because appending a 3 to 1 yields 13, which is prime; a(1) is not 1, because appending a 1 to 1 yields 11, which (although prime) contains more than one 1 in a row.
a(2) = 3 because appending a 3 to 22 yields 223 (prime), whereas appending a 1 produces the nonprime 221=13*17.

Crossrefs

Cf. A068120.

Sequence in context: A365991 A144149 A097005 * A123948 A329430 A188886

Adjacent sequences: A068005 A068006 A068007 * A068009 A068010 A068011

Keyword

nonn,base

Author

Robert G. Wilson v, Feb 22 2002

Extensions

Examples edited, and definition edited to match the rationale for a(1)=3 (not 1), by Jon E. Schoenfield, Sep 21 2013

Status

approved