login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A103804 Primes p such that both 2p +/- 21 are primes. 2
13, 19, 29, 31, 41, 59, 79, 89, 101, 109, 131, 179, 211, 239, 241, 271, 311, 331, 349, 409, 421, 449, 499, 509, 521, 541, 601, 619, 701, 751, 821, 839, 881, 1009, 1091, 1181, 1201, 1319, 1321, 1399, 1429, 1459, 1489, 1531, 1571, 1619, 1801, 1949, 1951 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..49.

FORMULA

p, 2p-21 and 2p+21 all are positive primes.

MATHEMATICA

Select[Range[2000], PrimeQ[ # ] && PrimeQ[2# + 21] && PrimeQ[2# - 21] &]

Select[Prime[Range[4, 500]], And@@PrimeQ[2#+{21, -21}]&] (* Harvey P. Dale, Dec 18 2012 *)

CROSSREFS

Cf. A103802, A103803.

Sequence in context: A227092 A123840 A258589 * A063640 A092104 A281483

Adjacent sequences:  A103801 A103802 A103803 * A103805 A103806 A103807

KEYWORD

nonn

AUTHOR

Zak Seidov, Feb 16 2005

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified March 28 15:38 EDT 2017. Contains 284243 sequences.