|
Search: id:A122170
|
|
|
| A122170 |
|
Number of primes p <= 2n such that p+n is also a prime. |
|
+0
2
|
|
| 1, 1, 1, 2, 1, 3, 0, 3, 1, 4, 1, 5, 0, 4, 1, 4, 1, 6, 0, 4, 1, 4, 0, 10, 0, 6, 1, 5, 1, 12, 0, 5, 0, 6, 1, 13, 0, 7, 1, 9, 1, 13, 0, 7, 1, 6, 0, 13, 0, 9, 1, 7, 0, 14, 0, 12, 1, 7, 1, 19, 0, 7, 0, 10, 1, 20, 0, 11, 1, 13, 1, 15, 0, 8, 0, 10, 1, 18, 0, 12, 1, 8, 0, 23, 0, 10, 1, 10, 0, 26, 0, 13, 0, 13
(list; graph; listen)
|
|
|
OFFSET
|
1,4
|
|
|
COMMENT
|
a(n)=0 for n in A007921.
|
|
EXAMPLE
|
a(12)=5 because only the 5 primes p=5,7,11,17,19 below 24 form other primes p+12 = 17,19,23,29,31.
|
|
MATHEMATICA
|
Table[Length[Select[Select[Range[2*n], PrimeQ], PrimeQ[ #+n]&]], {n, 100}] - Ryan Propper (rpropper(AT)stanford.edu), Nov 12 2006
|
|
CROSSREFS
|
Sequence in context: A004563 A098035 A079055 this_sequence A066029 A141198 A092093
Adjacent sequences: A122167 A122168 A122169 this_sequence A122171 A122172 A122173
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Lekraj Beedassy (blekraj(AT)yahoo.com), Aug 23 2006
|
|
EXTENSIONS
|
More terms from Ryan Propper (rpropper(AT)stanford.edu), Nov 12 2006
|
|
|
Search completed in 0.002 seconds
|
