A068648 Primes in which a string of 8's is sandwiched between two 1's.
11, 181, 188888881, 188888888888881, 18888888888888888888888888888888888888881, 188888888888888888888888888888888888888888888888888888888888888888888888888888888888888888881
Offset: 1
Examples
11 is also a member in which a string of 0 8's is there between two one's.
Links
- Patrick De Geest, PDP Reference Table - 181.
- Makoto Kamada, Prime numbers of the form 188...881.
- Index entries for primes involving repunits.
Programs
-
Maple
a := 1:b := 8: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[10FromDigits[PadRight[{1},n,8]]+1,{n,100}],PrimeQ] (* Harvey P. Dale, Jul 08 2020 *)
Extensions
More terms from Sascha Kurz, Mar 19 2002
Edited by Ray Chandler, Nov 04 2014
Comments