A227323 - OEIS

%I #16 Jul 14 2013 04:20:08

%S 11,1039,2099,4253,9433,9437,62983,62987,72229,72251,91121,386401,

%T 392269,392279,495589,495611,626617,663583,663587,754973,873553,

%U 908857,909301,909317,909319,909329,972137,1006309,1006331,1138393,1138409,1159201

%N Prime(k) such that each of the three preceding and also each of the three following primes are twin primes.

%C The union of sequences A069456 and A227063.

%C Prime(k) such that prime(k-i), i=1..3, and prime(k+i), i=1..3 are in A001097.

%p istwp := proc(n)

%p     if isprime(n) then

%p         if isprime(n+2) or isprime(n-2) then

%p             true;

%p         else

%p             false;

%p         end if;

%p     else

%p         false;

%p     end if;

%p end proc:

%p for i from 4 do

%p     p := ithprime(i) ;

%p     p1 := prevprime(p) ;

%p     if istwp(p1) then

%p         p2 := prevprime(p1) ;

%p         if istwp(p2) then

%p             p3 := prevprime(p2) ;

%p             if istwp(p3) then

%p                 p1 := nextprime(p) ;

%p                 if istwp(p1) then

%p                     p2 := nextprime(p1) ;

%p                     if istwp(p2) then

%p                         p3 := nextprime(p2) ;

%p                         if istwp(p3) then

%p                             printf("%d\n",p) ;

%p                         end if;

%p                     end if;

%p                 end if;

%p             end if;

%p         end if;

%p     end if;

%p end do: # _R. J. Mathar_, Jul 13 2013

%K nonn

%O 1,1

%A _Irina Gerasimova_, Jul 06 2013

%E Corrected by _R. J. Mathar_, Jul 13 2013