OFFSET
1,1
COMMENTS
The left side (most significant) digit must be 2 or 8. No odd digit can work because the least significant (right side) digit would then be even and thus the number would be divisible by 2. 6 will not work because the least significant (right side) digit would be 5 and thus the number would be divisible by 5. And 4 will not work because the resulting number is always divisible by 43. Harvey P. Dale, Jun 07 2023
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..21
MATHEMATICA
Select[Sort[Flatten[Table[FromDigits[Join[{l}, PadRight[{}, d, 7], {l-1}]], {l, {2, 8}}, {d, 500}]]], PrimeQ] (* Harvey P. Dale, Jun 06 2023 *)
PROG
(PARI) n10np1(n, d) = { local(x, y, k); for(x=1, n, for(k=1, 8, y=10^(x+1)*k+floor(10^x*d/9)*10+k-1; if(isprime(y), print1(y", ")) ) ) }
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Cino Hilliard, Jul 11 2005
EXTENSIONS
More terms from Harvey P. Dale, Jul 23 2012
STATUS
approved