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A108822 Primes such that the outer 2 digits are n and n+1 and all inner digits are 5, where 0 < n < 9. 0
859, 65557, 855555559, 6555555557, 855555555555555559, 85555555555555555559, 6555555555555555555557, 85555555555555555555555559, 85555555555555555555555555555555555555559, 6555555555555555555555555555555555555555555555557 (list; graph; refs; listen; history; text; internal format)
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

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Last modified August 8 17:55 EDT 2022. Contains 356016 sequences. (Running on oeis4.)