OFFSET
1,1
COMMENTS
Very similar to A031931.
3 and all prime(k+1) such that A001223(k) is divisible by 12. - Robert Israel, Jul 04 2018
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
FORMULA
2 NOT(|) (p+previous_prime(p))/2 AND 3 NOT(|) (p+previous_prime(p))/2
EXAMPLE
p = 223 => (p + previous_prime(p))/2 = (223 +211)/2 = 7*31;
p = 53 => (p + previous_prime(p))/2 = (53 + 51)/2 = 52 (divisible by 2).
MAPLE
count:= 1: Res:= 3:
p:= 3:
while count < 100 do
q:= p; p:= nextprime(p);
v:= (q+p)/2;
if igcd(v, 6)=1 then
count:= count+1;
Res:= Res, p;
fi
od:
Res; # Robert Israel, Jul 04 2018
PROG
(PARI) ok(n)={my(t=n+precprime(n-1)); n > 2 && isprime(n) && t%4 && t%3} \\ Andrew Howroyd, Jul 02 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Olivier Bélot, Apr 19 2018
STATUS
approved