A091417 - OEIS

A091417

Integers n which are not the difference of 2 integers A and B where A is less than or equal to n such that AB+1 and AB-1 are both primes. In other words, the product A*B cannot be the middle integer of a twin prime pair.

%I #1 Feb 19 2004 03:00:00

%S 8,9,10,15,18,20,30,40,51,58,60,65,75,96,100,110,120,170,195,240,250,

%T 260,315,330,345,390,540,630,750,780,910,1020,1720,1890

%N Integers n which are not the difference of 2 integers A and B where A is less than or equal to n such that AB+1 and AB-1 are both primes. In other words, the product A*B cannot be the middle integer of a twin prime pair.

%C Sequence may be finite. Next term after 1890 if it exists must be greater than 867750.

%e 8 is a member: 8 is the difference between these pairs of integers: (9-1) (10-2) (11-3) (12-4) (13-5) (14-6) (15-7) (16-8). Their products (9*1) (10*2), etc. plus and minus 1 are not primes and therefore the products cannot be the middle integers of twin prime sets.

%Y Cf. A090695, A091182, A091183. A091418.

%K nonn,fini

%O 1,1

%A William F. Sindelar (w_sindelar(AT)juno.com), Jan 05 2004