OFFSET
1,1
COMMENTS
Corresponding values of b-a: 1, 2, 2, 2, 4, 2, 4, 4, 2, 2, 2, 2, 4, 2, 2, 4, 2, 6, 4, 4, 2, 2, 2, 4, 4, 4, 2, 2, 6, 2, 6, 4, 6, 2, 6, 4, 2, 10. In most cases b-a = 2.
4-isolated primes according to the classification given in the paper on link (see Section 10). - Vladimir Shevelev, Oct 07 2012
LINKS
Zak Seidov, Table of n, a(n) for n = 1..2000
V. Shevelev, Ramanujan and Labos primes, their generalizations, and classifications of primes, J. Integer Seq. 15 (2012) Article 12.5.4
EXAMPLE
11 is the only prime in the interval [4*2, 4*3] = [8,12],
23 is the only prime in the interval [4*5, 4*7] = [20,28],
47 is the only prime in the interval [4*11, 4*13] = [44,52].
MATHEMATICA
a = 2; b = 3; s = {}; k = 4; Do[If[(p=NextPrime[k*a]) < k*b && NextPrime[p] > k*b, AppendTo[s, p]]; a = b; b = NextPrime[b], {100}]; s
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Oct 06 2012
STATUS
approved