This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A174213 Natural numbers n such that the concatenation n//1331 is a prime number. 7
 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 (list; graph; refs; listen; history; text; internal format)
 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 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 Sequence in context: A083966 A074326 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified October 21 08:47 EDT 2019. Contains 328292 sequences. (Running on oeis4.)