OFFSET
1,1
COMMENTS
Numbers of different digital types for n-digit primes are 1,2,4,11,...
LINKS
Peter J. C. Moses, Table of n, a(n) for n = 1..5000
EXAMPLE
The first 3-digit prime is 101=a(4).
The following 3-digit prime is 103. It does not have the same digital type as 101, since in 103 there are 3 distinct digits, but not in 101. So a(5)=103.
The next two primes 107 and 109 belongs to type 103.
Next consider 113. Here the first two digits are the same, but in 101 and 103 they are not. So 113 is a new type, and a(6)=113.
It remains to find the smallest prime of form XYY. It is 199=a(7).
Now we see that every 3-digit prime is of one of the 4 types a(4),a(5),a(6),a(7).
Next we consider the first 4-digit number a(8)=1009, etc.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Vladimir Shevelev, Jan 08 2016
EXTENSIONS
More terms from Peter J. C. Moses, Jan 08 2016
STATUS
approved