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A023240 Numbers n such that n and 10n + 9 are both prime. 8
2, 5, 7, 13, 17, 19, 23, 37, 41, 43, 47, 59, 61, 71, 73, 83, 101, 103, 127, 131, 139, 149, 157, 197, 199, 223, 233, 239, 257, 269, 271, 281, 293, 307, 311, 331, 349, 353, 373, 401, 409, 421, 433, 463, 467, 479, 491, 499, 503, 509, 541, 547, 563, 577, 587, 593, 607, 619 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

John Cerkan, Table of n, a(n) for n = 1..10000

MATHEMATICA

Select[Prime@ Range@ 120, PrimeQ[10 # + 9] &] (* Michael De Vlieger, Sep 12 2016 *)

PROG

(MAGMA) [ n: n in PrimesUpTo(700) | IsPrime(10*n+9) ]; // Vincenzo Librandi, Nov 20 2010

CROSSREFS

Subsequence of A102700.

Sequence in context: A261123 A249330 A069346 * A291284 A023204 A248606

Adjacent sequences:  A023237 A023238 A023239 * A023241 A023242 A023243

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified October 17 19:18 EDT 2019. Contains 328127 sequences. (Running on oeis4.)