OFFSET
1,3
MATHEMATICA
Table[k = 0; While[!PrimeQ[(3^n - k)*3^n + 1], k++]; k, {n, 72}]
lk[n_]:=Module[{c=3^n, k=1}, While[!PrimeQ[(c-k)*c+1], k++]; k]; Array[lk, 70] (* Harvey P. Dale, Jul 15 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Nov 24 2011
STATUS
approved