A064220 Least k such that k*11^n +/- 1 are twin primes.

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

Author

Robert G. Wilson v, Sep 21 2001

Keywords

• nonn

Crossrefs

Cf. A063983, A064213, A064214, A064215. A064217, A064218, A064221.

Programs

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 *)

Extensions

Offset corrected by Georg Fischer, May 01 2022