This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A068008 #10 Sep 23 2013 12:59:26 %S A068008 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, %T A068008 153,163,1,297,103,323,61,127,113,31,127,353,67,841,187,9,21,179,429, %U A068008 127,97,3,319,11,51,39,191,33,3,41,151,39,47,169,787,401,57,441,571 %N 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. %C A068008 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 %e A068008 a(0) = 2 because appending 2 to a zero-length string (i.e., 0 0's) yields 2, which is prime. %e A068008 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. %e A068008 a(2) = 3 because appending a 3 to 22 yields 223 (prime), whereas appending a 1 produces the nonprime 221=13*17. %Y A068008 Cf. A068120. %K A068008 nonn,base %O A068008 0,1 %A A068008 _Robert G. Wilson v_, Feb 22 2002 %E A068008 Examples edited, and definition edited to match the rationale for a(1)=3 (not 1), by _Jon E. Schoenfield_, Sep 21 2013