|
|
A269256
|
|
Chen primes p such that there are Chen primes p > q > r in arithmetic progression.
|
|
2
|
|
|
7, 11, 17, 19, 23, 29, 31, 41, 47, 53, 59, 67, 71, 83, 89, 101, 107, 113, 127, 131, 137, 139, 149, 167, 179, 181, 191, 197, 199, 211, 227, 233, 239, 251, 257, 263, 269, 281, 293, 307, 311, 317, 347
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
Green & Tao prove that this sequence is infinite.
|
|
LINKS
|
|
|
EXAMPLE
|
19 is in the sequence since 3 < 11 < 19, 19 - 11 = 11 - 3, all three are prime, and 3+2, 11+2, and 19+2 are each either prime or semiprime.
|
|
PROG
|
(PARI) issemi(n)=bigomega(n)==2
ischen(n)=isprime(n) && (isprime(n+2) || issemi(n+2))
is(n)=if(!ischen(n), return(0)); forprime(p=2, n-4, if((p+n)%4==2 && ischen(p) && ischen((p+n)/2), return(1))); 0
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|