A064281 Least k such that k*10^n+1, k*10^n+3, k*10^n+7 and k*10^n+9 are all prime.

4, 1, 1, 13, 676, 283, 14311, 12022, 27346, 14965, 3427, 100942, 12370, 1237, 3274, 42382, 18619, 4570, 457, 434869, 203362, 305491, 213742, 436831, 217198, 168586, 258214, 215737, 1312441, 272848, 744082, 2059111, 351055, 712333, 1880302

Offset: 0

Author

Robert G. Wilson v, Oct 14 2001

Keywords

• nonn

Links

• Sean A. Irvine, Table of n, a(n) for n = 0..50

Programs

Mathematica

Do[k = 1; While[ !PrimeQ[k*10^n + 1] || !PrimeQ[k*10^n + 3] || !PrimeQ[k*10^n + 7] || !PrimeQ[k*10^n + 9], k++ ]; Print[k], {n, 0, 20} ]
lk[n_]:=Module[{k=1},While[!AllTrue[k*10^n+{1,3,7,9},PrimeQ],k++];k]; Array[lk,40,0] (* Harvey P. Dale, Sep 03 2024 *)