A068813 Primes with a 3 followed by 1's.
31, 311, 311111, 31111111111, 311111111111, 31111111111111, 31111111111111111111111111111111111, 311111111111111111111111111111111111111111111111, 31111111111111111111111111111111111111111111111111111
Offset: 1
Examples
Digit 3 followed by rep-units of length 1,2,5,10,11,13,34,47,52,77,88,...
Links
- Makoto Kamada, Prime numbers of the form 311...11.
- H. C. Williams, Some primes with interesting digit patterns, Math. Comp. vol 32 no 144 (1978) pp 1306-1310, Table 2, r=3.
- Index entries for primes involving repunits
Programs
-
Mathematica
Select[Table[FromDigits[PadRight[{3},n,1]],{n,2,100}],PrimeQ] (* Harvey P. Dale, Nov 18 2012 *) -
PARI
for(n=1,200, if(isprime(3*10^n+(10^(n)-1)/9)==1,print1(3*10^n+(10^(n)-1)/9,",")))
Extensions
More terms from Benoit Cloitre, Mar 09 2002
One additional term from Harvey P. Dale, Nov 18 2012