A108822 Primes such that the outer 2 digits are n and n+1 and all inner digits are 5, where 0 < n < 9.

859, 65557, 855555559, 6555555557, 855555555555555559, 85555555555555555559, 6555555555555555555557, 85555555555555555555555559, 85555555555555555555555555555555555555559, 6555555555555555555555555555555555555555555555557

Offset

1,1

Links

Table of n, a(n) for n=1..10.

Formula

a(x) = 10^(x+1)*n+floor(10^x*5/9)*10+n+1. Output if a(x) is prime.

Mathematica

Select[Sort[Flatten[Table[FromDigits[Join[{n}, PadRight[{}, i, 5], {n+1}]], {n, {2, 6, 8}}, {i, 50}]]], PrimeQ] (* Harvey P. Dale, Aug 02 2015 *)

Prog

(PARI) n10np1(n) = { local(x, y, k); for(x=1, n, for(k=1, 8, y=10^(x+1)*k+floor(10^x*5/9)*10+k+1; if(isprime(y), print1(y", ")) ) ) }

Crossrefs

Sequence in context: A345801 A183628 A187281 * A278156 A249461 A292626

Adjacent sequences: A108819 A108820 A108821 * A108823 A108824 A108825

Keyword

easy,nonn,base

Author

Cino Hilliard, Jul 11 2005

Extensions

One more term (a(10)) from Harvey P. Dale, Aug 02 2015

Status

approved