OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..27
FORMULA
a(x) = 10^(x+1)*n+floor(10^x*4/9)*10+n+1. Output if a(x) is prime.
MATHEMATICA
Select[Sort[Flatten[Table[FromDigits[Join[{n}, PadRight[{}, m, 4], {n+1}]], {n, 8}, {m, 40}]]], PrimeQ] (* Harvey P. Dale, Mar 17 2019 *)
PROG
(PARI) n10np1(n) = { local(x, y, k); for(x=1, n, for(k=1, 8, y=10^(x+1)*k+floor(10^x*4/9)*10+k+1; if(isprime(y), print1(y", ")) ) ) }
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Cino Hilliard, Jul 11 2005
STATUS
approved