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A064220
Least k such that k*11^n +/- 1 are twin primes.
3
4, 18, 12, 12, 120, 168, 72, 78, 810, 312, 90, 138, 270, 948, 408, 192, 960, 1920, 738, 4698, 810, 1872, 6978, 2058, 3222, 570, 870, 390, 9708, 14118, 9378, 6822, 8730, 2250, 1008, 8052, 732, 5400, 2910, 5982, 2688, 16758, 1908, 258, 762, 1488, 12678
OFFSET
0,1
MATHEMATICA
Do[ k = 1; While[ ! PrimeQ[ k*11^n + 1 ] || ! PrimeQ[ k*11^n - 1 ], k++ ]; Print[ k ], {n, 0, 50} ]
lk[n_]:=Module[{c=11^n, k=1}, While[!PrimeQ[k*c+1]||!PrimeQ[k*c-1], k++]; k]; Array[lk, 50, 0] (* Harvey P. Dale, Jun 15 2019 *)
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Sep 21 2001
EXTENSIONS
Offset corrected by Georg Fischer, May 01 2022
STATUS
approved