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A306855 Primes of the form 10^i + 10^j - 1. 1
19, 109, 199, 1009, 1999, 10009, 10099, 100999, 199999, 1000099, 1000999, 19999999, 1000000009, 1000009999, 1000099999, 1009999999, 10000000999, 10000099999, 10999999999, 100999999999, 1000000009999, 1000000999999, 1099999999999, 10000000000099, 10009999999999, 100000000000099, 100000009999999 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Primes p such that p+1 is in A052216.

Primes of the following form in base 10: 1, followed by 0 or more 0's, then 1 or more 9's.

LINKS

Robert Israel, Table of n, a(n) for n = 1..2000

MAPLE

select(isprime, [seq(seq(10^n+10^m-1, m=1..n), n=1..15)]);

MATHEMATICA

Select[Flatten[Table[FromDigits[Join[PadRight[{1}, n, 0], PadRight[{}, m, 9]]], {n, 20}, {m, 20}]], PrimeQ]//Sort (* Harvey P. Dale, May 15 2021 *)

CROSSREFS

Cf. A052216. Subsequence of A199329.

Sequence in context: A282324 A264825 A142322 * A243761 A184056 A280628

Adjacent sequences:  A306852 A306853 A306854 * A306856 A306857 A306858

KEYWORD

nonn,base

AUTHOR

Robert Israel, Mar 13 2019

STATUS

approved

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Last modified July 1 16:18 EDT 2022. Contains 354973 sequences. (Running on oeis4.)