A103688 a(n)=n if for the least k such that k*n -1 or +1 is prime, k*n -1 and k*n +1 are twin primes or a(n)=0 if only one of k*n -1 and k*n +1 is prime for the least k.

1, 2, 3, 4, 6, 0, 0, 9, 0, 0, 12, 0, 0, 15, 0, 0, 18, 0, 0, 21, 0, 23, 0, 25, 0, 0, 0, 0, 30, 0, 0, 0, 0, 0, 36, 0, 0, 0, 0, 0, 42, 0, 0, 0, 46, 47, 0, 0, 50, 51, 0, 0, 0, 0, 0, 0, 0, 0, 60, 0, 0, 0, 0, 0, 0, 0, 0, 69, 0, 0, 72, 0, 0, 75, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 94, 0, 96, 0, 0