A108833 Primes such that the outer 2 digits are n and n-1 and all inner digits are 5, where 0 < n < 9.

251, 857, 2551, 45553, 255551, 2555551, 45555553, 855555557, 2555555555551, 45555555555555555553, 45555555555555555555555555555555553, 4555555555555555555555555555555555555555555555555555553

Offset

1,1

Comments

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

Links

Harvey P. Dale, Table of n, a(n) for n = 1..19 (* All terms with less than 1000 digits. *)

Mathematica

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 *)

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

Sequence in context: A001135 A052232 A179231 * A228672 A339182 A008917

Adjacent sequences: A108830 A108831 A108832 * A108834 A108835 A108836

Keyword

easy,nonn,base

Author

Cino Hilliard, Jul 11 2005

Status

approved