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

Offset: 1

Author

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

Keywords

• base
• nonn

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.

Examples

			61331 = prime(6169) => a(1) = 6.
81331 = prime(7958) => a(2) = 8.
		

Crossrefs

A168327, A168417, A173836

Programs

Mathematica

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

PARI

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