A174355 - OEIS

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A174355

Natural numbers n such that the concatenations n//1331 and 1331//n are prime numbers.

53, 57, 153, 249, 279, 329, 333, 339, 347, 381, 399, 431, 471, 489, 641, 647, 711, 821, 851, 923, 959, 987, 1169, 1239, 1313, 1383, 1479, 1547, 1563, 1589, 1611, 1653, 1677, 1709, 1773, 1863, 1887, 1973, 2031, 2067

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

See comments and references for A173836, A174213.

Intersection of A173579 and A174213. - Michel Marcus, Aug 27 2013

REFERENCES

Marcus du Sautoy: Die Musik der Primzahlen. Auf den Spuren des groessten Raetsels der Mathematik, Beck, Muenchen 2004

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

531331 = prime(43928), 133153 = prime(12427), 53 is smallest term of sequence.

MATHEMATICA

Select[Range[2100], AllTrue[{#*10^4+1331, 1331*10^IntegerLength[#]+#}, PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Aug 21 2015 *)

PROG

(PARI) isok(n) = isprime(n*10^4 + 1331) && isprime(1331*10^(length(Str(n))) + n); \\ Michel Marcus, Aug 27 2013

CROSSREFS

Cf. A168327, A168417, A173836, A174213, A174260.

Sequence in context: A344798 A294739 A317970 * A095549 A095539 A095529

Adjacent sequences: A174352 A174353 A174354 * A174356 A174357 A174358

KEYWORD

base,nonn

AUTHOR

Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Mar 17 2010

STATUS

approved