A108826 Primes such that the outer 2 digits are n and n+1 and all inner digits are 8, where 0 < n < 9.

283, 28888883, 88888888888889, 88888888888888889, 28888888888888888888888888883, 6888888888888888888888888888888887, 88888888888888888888888888888888889, 6888888888888888888888888888888888888888888888888888888888888888888888887, 28888888888888888888888888888888888888888888888888888888888888888888888883

Offset

1,1

Links

Table of n, a(n) for n=1..9.

Formula

a(x) = 10^(x+1)*n+floor(10^x*8/9)*10+n+1. Output if a(x) is prime.

Mathematica

Select[FromDigits/@Flatten[Table[Join[{n}, PadRight[{}, k, 8], {n+1}], {n, 8}, {k, 100}], 1], PrimeQ]//Sort (* Harvey P. Dale, Oct 09 2018 *)

Prog

(PARI) n10np1(n) = { local(x, y, k); for(x=1, n, for(k=1, 8, y=10^(x+1)*k+floor(10^x*8/9)*10+k+1; if(isprime(y), print1(y", ")) ) ) }

Crossrefs

Sequence in context: A064964 A372402 A263670 * A285890 A356219 A061310

Adjacent sequences: A108823 A108824 A108825 * A108827 A108828 A108829

Keyword

easy,nonn,base

Author

Cino Hilliard, Jul 11 2005

Extensions

More terms from Harvey P. Dale, Oct 09 2018

Status

approved