A174441 - OEIS

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A174441

Primes p such that the concatenations p//1331 and 1331//p are both prime numbers (for naturals see A174355).

53, 347, 431, 641, 647, 821, 1709, 1973, 2081, 2591, 2657, 2963, 4073, 4139, 4643, 4787, 5039, 5483, 5657, 6029, 6791, 6917, 6959, 7127, 7673, 8273, 8693, 8807, 8849, 9221, 9311, 9689, 10139, 10457, 11423, 12503, 12743, 13619, 13913, 14549

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

OFFSET

1,1

COMMENTS

See comments and references for A173836, A174213.

LINKS

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

EXAMPLE

531331 = prime(43928), 133153 = prime(12427) => p(1) = 53 = prime(16).

3471331 = prime(248286), 1331347 = prime(102237) => p(2) = 347 = prime(69).

139131331 = prime(7865788), 133113913 = prime(7544750) => p(39) = 13913 = prime(1645).

MATHEMATICA

Select[Prime[Range[2000]], AllTrue[{#*10^4+1331, 1331*10^IntegerLength[ #]+#}, PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, May 08 2016 *)

PROG

(PARI) isok(n) = isprime(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, A174355.

Sequence in context: A140042 A239747 A261335 * A094249 A244771 A074836

Adjacent sequences: A174438 A174439 A174440 * A174442 A174443 A174444

KEYWORD

base,nonn

AUTHOR

Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Mar 20 2010

STATUS

approved