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%I #16 Sep 06 2023 19:21:26
%S 251,857,2551,45553,255551,2555551,45555553,855555557,2555555555551,
%T 45555555555555555553,45555555555555555555555555555555553,
%U 4555555555555555555555555555555555555555555555555555553
%N Primes such that the outer 2 digits are n and n-1 and all inner digits are 5, where 0 < n < 9.
%C All terms must start with 2, 4, or 8 so that each term ends with 1, 3, or 7. - _Harvey P. Dale_, Sep 06 2023
%H Harvey P. Dale, <a href="/A108833/b108833.txt">Table of n, a(n) for n = 1..19</a> (* All terms with less than 1000 digits. *)
%t Select[Sort[Flatten[Table[FromDigits[Join[{n},PadRight[{},k,5],{n-1}]],{n,{2,4,8}},{k,60}]]],PrimeQ] (* _Harvey P. Dale_, Sep 06 2023 *)
%o (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",")) ) ) }
%K easy,nonn,base
%O 1,1
%A _Cino Hilliard_, Jul 11 2005
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