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A228377 Primes of the form XYYYYYYYX, where Y is a single digit. 1
188888881, 199999991, 322222223, 355555553, 722222227, 17333333317, 19555555519, 21444444421, 27888888827, 29111111129, 31333333331, 31555555531, 31666666631, 39444444439, 41999999941, 43222222243, 43666666643, 47999999947, 49333333349, 49555555549 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

MATHEMATICA

f[n_]: = Block[{len = Floor[Log[10, n] + 1]}, Select[10^(7 + len) n + 10^len Table[k (10^7 - 1) / 9, {k, 9}] + n, PrimeQ@#&]]; Array[f, 1000]//Flatten

PROG

(MAGMA) m:=7; [p: d in [1..9], n in [1..80 by 2] | IsPrime(p) where p is n*(10^(m+t)+1)+d*10^t*(10^m-1) div 9 where t is #Intseq(n)]; //

CROSSREFS

Cf. A154270, A214290, A162423, A214702, A214291.

Sequence in context: A061440 A064593 A084304 * A178565 A195902 A181321

Adjacent sequences:  A228374 A228375 A228376 * A228378 A228379 A228380

KEYWORD

nonn,base

AUTHOR

Vincenzo Librandi, Sep 12 2013

STATUS

approved

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Last modified September 19 00:22 EDT 2021. Contains 347549 sequences. (Running on oeis4.)