A128942 - OEIS

%I #8 Oct 01 2013 21:35:21

%S 1,2,4,9,537,1322,1476

%N Numbers n such that the next prime exceeding 10^n is a twin prime member.

%C A003617(a(n)) is in A001097 (Twin primes).

%e For n=2, 10^2 = 100. The first prime > 100 is 101 which is a member of the twin prime pair 101,103.

%t tpQ[n_]:=Module[{pr=NextPrime[10^n]},Or@@PrimeQ[{pr-2,pr+2}]]; Select[ Range[ 1500],tpQ] (* _Harvey P. Dale_, Aug 05 2012 *)

%o (PARI) g(n)=for(x=1,n,y=nextprime(10^x);if(ispseudoprime(y+2),print1(x",")))

%K hard,more,nonn

%O 1,2

%A _Cino Hilliard_, Apr 28 2007

%E Edited by _Ray Chandler_, May 12 2007

%E a(6), a(7) from _Donovan Johnson_, Feb 21 2008