A284891 Concatenation of the numbers from 3 to n.

3, 34, 345, 3456, 34567, 345678, 3456789, 345678910, 34567891011, 3456789101112, 345678910111213, 34567891011121314, 3456789101112131415, 345678910111213141516, 34567891011121314151617, 3456789101112131415161718, 345678910111213141516171819

Offset: 3

Author

XU Pingya, Apr 05 2017

Keywords

• base
• nonn
• easy

Comments

The a(3) = 3, a(19) = 345678910111213141516171819 are primes in this sequence (for n < 2800).

Links

• Eric Weisstein's World of Mathematics, Consecutive Number Sequences

Crossrefs

Cf. A089987, A262571.