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

1, 5, 14, 406, 1118, 4934

Offset

1,2

Comments

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

Links

Table of n, a(n) for n=1..6.

Example

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

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 *)

Prog

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

Crossrefs

Sequence in context: A317691 A067857 A027832 * A156219 A000331 A353610

Adjacent sequences: A128943 A128944 A128945 * A128947 A128948 A128949

Keyword

hard,more,nonn

Author

Cino Hilliard, Apr 28 2007

Extensions

Edited by Ray Chandler, May 12 2007

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

Status

approved