OFFSET
1,1
COMMENTS
Corresponding values of b-a: 2, 2, 2, 2, 2, 2, 2, 2, 2, 4, 2, 2, 2, 2, 2, 6, 4, 4, 2, 2, 2, 2, 6, 2, 2, 2, 4, 2, 2, 6, 2, 2, 4, 4, 2, 6. In most cases b-a = 2. Smallest n for which b-a = 2(2)26: 1, 10, 16, 62, 119, 414, 939, 2565, 1349, 1042, 10470, 22211, 23553. Also, at n = 43461, b-a = 32.
LINKS
Zak Seidov, Table of n, a(n) for n = 1..10000
EXAMPLE
89 is the only prime in the interval [5*17, 5*19] = [85,95],
211 is the only prime in the interval [5*41, 5*43] = [205,215],
359 is the only prime in the interval [5*71, 5*73] = [355,365].
MATHEMATICA
a = 2; b = 3; s = {}; k = 5; 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 07 2012
STATUS
approved