A306475 Smallest nonprime number <= 10^n (n>=1) with maximum distance from a prime.

9, 93, 897, 9569, 31433, 492170, 4652430, 47326803, 436273150, 4302407536, 42652618575, 738832928197, 7177162612050, 90874329411895, 218209405436996, 1693182318746937, 80873624627235459, 804212830686678390

Offset: 1

Author

David Cobac, Feb 18 2019

Keywords

• nonn
• more

Comments

Each number is a mean of two consecutive primes.

Since, except 2, primes are odd numbers, this mean is an integer.

Examples

			For n=1: first prime numbers are 2, 3, 5, 7 and 11. Maximum difference between two consecutive primes is 4 between 7 and 11 thus a(1)=9.
For n=4: maximum difference between two primes less than 10^4 is 36, which occurs once: between 9551 and 9587. a(4)=(9551 + 9587)/2 = 9569.
		

Crossrefs

Cf. A000040, A001223, A087378, A282690.

Extensions

More terms (using the b-file at A002386) from Jon E. Schoenfield, Feb 19 2019