A104206 - OEIS

%I #13 Aug 17 2017 23:43:09

%S 27,1197,101997,10099973,1000799991,100003999983,10000039999991,

%T 1000001999999989,100000007999999937,10000000079999999967,

%U 1000000001999999999977,100000000003999999999989,10000000000399999999999971,1000000000003799999999999973

%N Concatenation of the smallest and the largest n-digit primes.

%H Harvey P. Dale, <a href="/A104206/b104206.txt">Table of n, a(n) for n = 0..499</a>

%H Chris Caldwell <a href="http://www.utm.edu/research/primes/lists/small/10000.txt">The First 10,000 Primes</a>

%e 27 is obtained by concatenating the smallest 1-digit prime and the largest 1-digit prime.

%e 1197 is obtained by concatenating the smallest 2-digit prime and the largest 2-digit prime.

%p for n from 0 to 30 do for m from 1 to 10^(n+1)-1 do if isprime(10^n + m) then printf(`%d`,10^n+m); break; fi: od: for m from 1 to 10^(n+1)-1 do if isprime(10^(n+1) - m) then printf(`%d`,10^(n+1)-m); break; fi: od: printf(`,`): od: # _James A. Sellers_, May 02 2005

%t FromDigits/@Table[Flatten[{IntegerDigits[NextPrime[10^n]],IntegerDigits[ NextPrime[ 10^(n+1),-1]]}],{n,0,15}] (* _Harvey P. Dale_, Aug 06 2013 *)

%K nonn,base,less

%O 0,1

%A _Parthasarathy Nambi_, Apr 01 2005

%E More terms from _James A. Sellers_, May 02 2005

%E Edited by _Charles R Greathouse IV_, Apr 27 2010

%E More terms from _Harvey P. Dale_, Aug 06 2013