A128946 Numbers n such that the largest prime < 10^n is a twin prime member.

1, 5, 14, 406, 1118, 4934

Offset: 1

Author

Cino Hilliard, Apr 28 2007

Keywords

• hard
• more
• nonn

Comments

A003618(a(n)) is in A001097 (Twin primes).

Examples

			For n=1, 10^1 = 10. 7, the greatest prime < 10, is a member of the twin prime pair 5,7.
		

Programs

Mathematica

Select[Range[410],PrimeQ[NextPrime[10^#,-1]-2]&] (* The program generates the first four terms of the sequence. *) (* Harvey P. Dale, Jul 26 2024 *)

PARI

g(n)=for(x=1,n,y=precprime(10^x);if(ispseudoprime(y-2),print1(x",")))

Extensions

Edited by Ray Chandler, May 12 2007

a(5), a(6) from Donovan Johnson, Feb 21 2008