%I #19 Apr 21 2017 20:44:50
%S 3,34,345,3456,34567,345678,3456789,345678910,34567891011,
%T 3456789101112,345678910111213,34567891011121314,3456789101112131415,
%U 345678910111213141516,34567891011121314151617,3456789101112131415161718,345678910111213141516171819
%N Concatenation of the numbers from 3 to n.
%C The a(3) = 3, a(19) = 345678910111213141516171819 are primes in this sequence (for n < 2800).
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ConsecutiveNumberSequences.html">Consecutive Number Sequences</a>
%Y Cf. A089987, A262571.
%K base,nonn,easy
%O 3,1
%A _XU Pingya_, Apr 05 2017