OFFSET
1,2
FORMULA
EXAMPLE
For n = 8, the 8th prime pair is (71, 73), the prime before 71 is 67 and prime after 73 is 79. So a(8) = 67 + 79 - 71 - 73 = 2.
MATHEMATICA
Map[#1 + #4 - (#2 + #3) & @@ # &, Select[Partition[Prime@ Range[500], 4, 1], And[#3 - #2 == 2] & @@ # &]] (* Michael De Vlieger, Jun 30 2018 *)
PROG
(PARI) {
print1(2+7-(5+3)", ");
forstep(n=6, 100, 6,
if(isprime(n-1)&&isprime(n+1),
a=precprime(n-2); b=nextprime(n+2);
print1(a+b-2*n", ")
)
)
}
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Dimitris Valianatos, Jun 21 2018
EXTENSIONS
Definition clarified by Jianing Song, Jun 22 2018
STATUS
approved