OFFSET
1,4
COMMENTS
Conjecture: a(n) > 0 for all n >= 3. - Dmitry Kamenetsky, Mar 18 2019
FORMULA
a(n) = A071127(prime(n)). - Michel Marcus, Mar 19 2019
EXAMPLE
2*7 + 3 = 17 and 2*7 + 5 = 19 are prime. Hence a(4) = 2.
PROG
(PARI) a(n) = my(s=0, p=prime(n)); forprime(i=1, p-1, s += isprime(2*p+i)); s; \\ Michel Marcus, Mar 19 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Dmitry Kamenetsky, Mar 18 2019
STATUS
approved