OFFSET
1,2
COMMENTS
Assuming a Bertrand-like result for twin primes, that for every n > 3 there is a prime n < p < 2n such that either p-2 or p+2 is prime, the only missing terms are 1, 2, 4, 6, and 9.
FORMULA
Conjecturally, a(n) = n+4 for n > 5. This holds at least up to 2^500.
CROSSREFS
KEYWORD
nonn
AUTHOR
Charles R Greathouse IV, Jun 21 2012
STATUS
approved