A174213 - OEIS

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A174213

Natural numbers n such that the concatenation n//1331 is a prime number.

6, 8, 9, 23, 29, 30, 32, 39, 42, 45, 53, 57, 65, 80, 92, 95, 101, 102, 108, 113, 116, 128, 141, 144, 153, 161, 182, 183, 186, 200, 206, 216, 218, 219, 225, 239, 245, 249, 260, 266, 270, 273, 279, 281, 282, 296, 311, 314, 318, 321

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OFFSET

1,1

COMMENTS

n is no multiple of 11 as 1331 = 11^3.

Necessarily n = 3 * k or n = 3 * k + 2, but not n = 3 * k + 1, because sod(1331) = 8.

Sequence is infinite, Dirichlet's prime number theorem for naturals of the form n * 10^4 + 1331.

For prefixed 1331 and references see A173836.

LINKS

Table of n, a(n) for n=1..50.

EXAMPLE

61331 = prime(6169) => a(1) = 6.

81331 = prime(7958) => a(2) = 8.

MATHEMATICA

Select[Range[400], PrimeQ[#*10^4+1331]&] (* Harvey P. Dale, Jan 17 2019 *)

PROG

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

CROSSREFS

A168327, A168417, A173836

Sequence in context: A074326 A342649 A254321 * A284990 A238621 A099102

Adjacent sequences: A174210 A174211 A174212 * A174214 A174215 A174216

KEYWORD

base,nonn

AUTHOR

Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Mar 12 2010

STATUS

approved