This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A276741 Integers n such that 10^n + 5^n + 2^n is a prime. 0
 0, 1, 7, 31, 37, 71, 235, 515, 1199, 1815, 6587, 30429, 35589, 42147, 58571 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Corresponding primes of the form 10^n + 5^n + 2^n are {3, 17, 10078253, 10000000004656612873079540061773,  10000000000072759576141834396472156597, 100000000000000000000042351647362715016953416125036343281344004402684973, ...} a(12) > 10000 if it exists. - Felix Fröhlich, Sep 17 2016 a(16) > 100000. - Robert Price, Dec 29 2016 LINKS MATHEMATICA Do[f=10^n+5^n+2^n; If[PrimeQ[f], Print[{n, f}]], {n, 1, 2000}] PROG (PARI) is(n) = ispseudoprime(10^n+5^n+2^n) \\ Felix Fröhlich, Sep 17 2016 CROSSREFS Cf. A125706. Sequence in context: A272201 A325423 A309381 * A000696 A171733 A128028 Adjacent sequences:  A276738 A276739 A276740 * A276742 A276743 A276744 KEYWORD hard,more,nonn AUTHOR René Gy, Sep 16 2016 EXTENSIONS a(11) from Felix Fröhlich, Sep 17 2016 a(12)-a(15) from Robert Price, Dec 29 2016 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 18 23:39 EDT 2019. Contains 328211 sequences. (Running on oeis4.)