The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A156983 Primes of the form 2^k + 21. 1
 23, 29, 37, 53, 149, 277, 2069, 32789, 65557, 524309, 17592186044437, 281474976710677, 2251799813685269, 4503599627370517, 2305843009213693973, 11692013098647223345629478661730264157247460343829 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 23 = 2^1 + 21 is in the sequence; 29 = 2^3 + 21 is in the sequence. MATHEMATICA Delete[Union[Table[If[PrimeQ[2^n + 21], 2^n + 21, 0], {n, 1, 500}]], 1] PROG (MAGMA) [ a: n in [1..200] | IsPrime(a) where a is 2^n+21 ]; // Vincenzo Librandi, Nov 27 2010 CROSSREFS Cf. A019434 (2^(2^n)+1), A057733 (2^n+3), A123250 (2^n+5). Sequence in context: A353286 A101784 A101802 * A230456 A174196 A144226 Adjacent sequences:  A156980 A156981 A156982 * A156984 A156985 A156986 KEYWORD nonn AUTHOR Edwin Dyke (ed.dyke(AT)btinternet.com), Feb 20 2009 EXTENSIONS More terms from Vincenzo Librandi, Apr 29 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 26 12:28 EDT 2022. Contains 354882 sequences. (Running on oeis4.)