The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A094475 Primes of form 2^n + 5^n. 5
 2, 7, 29, 641 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 2^n+p^n is prime if n=0;or n=1 and p is a smaller of twin primes; or n=2 and 4+p^2 is prime; or n=3 and 8+p^3 is prime etc. Several conditions have to be satisfied to get a modest number of terms... n must be zero or a power of two.  Checked n being powers of two through 2^22. Thus a(5) > 10^5800000. Primes of this magnitude are rare (about 1 in 13.4 million), so chance of finding one is remote with today's computer algorithms and speeds. - Robert Price, May 02 2013 LINKS EXAMPLE For n=4, p=2^4+5^4=641, so p can be prime even when the exponent is not a prime. MATHEMATICA Select[Table[2^n+5^n, {n, 0, 5000}], PrimeQ] (* Harvey P. Dale, May 28 2014 *) PROG (MAGMA) [ a: n in [0..2100] | IsPrime(a) where a is 5^n+2^n]; // Vincenzo Librandi, Nov 18 2010 CROSSREFS Cf. A094473, A094474, A082101, A094476. Sequence in context: A003437 A192410 A270518 * A093034 A125174 A270526 Adjacent sequences:  A094472 A094473 A094474 * A094476 A094477 A094478 KEYWORD nonn,easy AUTHOR Labos Elemer, Jun 01 2004 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 August 10 01:20 EDT 2020. Contains 336360 sequences. (Running on oeis4.)