A036229 Smallest n-digit prime containing only digits 1 or 2 or -1 if no such prime exists.
2, 11, 211, 2111, 12211, 111121, 1111211, 11221211, 111112121, 1111111121, 11111121121, 111111211111, 1111111121221, 11111111112221, 111111112111121, 1111111112122111, 11111111111112121, 111111111111112111, 1111111111111111111, 11111111111111212121
Offset: 1
Links
- Chai Wah Wu, Table of n, a(n) for n = 1..1000 (terms n=1..400 from Alois P. Heinz)
- Robert G. Wilson v, Comments and first 100 terms
Programs
-
Mathematica
Do[p = (10^n - 1)/9; k = 0; While[ ! PrimeQ[p], k++; p = FromDigits[ PadLeft[ IntegerDigits[ k, 2], n] + 1]]; Print[p], {n, 1, 20}] Table[Min[Select[ FromDigits/@Tuples[{1,2},n],PrimeQ]],{n,20}] (* Harvey P. Dale, Feb 05 2014 *) -
Python
from sympy import isprime def A036229(n): k, r, m = (10**n-1)//9, 2**n-1, 0 while m <= r: t = k+int(bin(m)[2:]) if isprime(t): return t m += 1 return -1 # Chai Wah Wu, Aug 18 2021
Extensions
Edited by N. J. A. Sloane and Robert G. Wilson v, May 03 2002
Escape clause added by Chai Wah Wu, Aug 18 2021
Comments