OFFSET
1,1
COMMENTS
The next term has 199 9's sandwiched between the starting and ending 1.
LINKS
Patrick De Geest, PDP Reference Table - 191.
Makoto Kamada, Prime numbers of the form 199...991.
EXAMPLE
11 is also a member in which a string of 0 9's is there between two one's.
MAPLE
a := 1:b := 9:i := 1:for n from 0 to 500 do c := a+10*(10^n-1)/9*b+10^(n+1)*a; if(isprime(c)) then d[i] := c; i := i+1; end if; end do:q := seq(d[j], j=1..i-1);
MATHEMATICA
Select[Table[FromDigits[Join[{1}, Table[9, {i}], {1}]], {i, 0, 200}], PrimeQ]
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Feb 28 2002
EXTENSIONS
More terms from Sascha Kurz and Harvey P. Dale, Mar 19 2002
Edited by Ray Chandler, Nov 04 2014
STATUS
approved