%I
%S 4,6,18,24,138,60,150,720,150,234,138,966,138,420,60,1584,420,60,1830,
%T 1134,162,1080,1482,684,240,10074,3378,3300,2742,984,2400,4050,5262,
%U 3510,3378,960,3612,516,6840,6474,4680,4950,12612,7986,4290,8046,5208
%N Least k such that k*7^n +/ 1 are twin primes.
%t Do[ k = 1; While[ ! PrimeQ[ k*7^n + 1 ]  ! PrimeQ[ k*7^n  1 ], k++ ]; Print[ k ], {n, 0, 50} ]
%Y Cf. A063983.
%K nonn
%O 1,1
%A _Robert G. Wilson v_, Sep 21 2001
