OFFSET
1,1
COMMENTS
Indices of primes are: 1, 5, 25, 110, 840, 369, 3745, 6329, 4142, 9990, 56934, 42502, 87392, 306589, 344750, 336038, 407897, 2031387, 6058935, 2273894, 6223604, 18062361, 31253527, 40636901, 44264857, 94194169, 112738722, 128926127, 19290534, 258502581, 413356835. Notice that indices (and primes) are not necessarily monotonically increasing. Cf. A133478 (semiprime gaps without primes).
EXAMPLE
a(1)=2 because gap=3-2=1 and between 2 and 3 there is no semiprimes,
a(2)=11 because gap=11-13=2 and between 11 and 13 there is no semiprimes,
a(3)=97 because gap=97-101=4 and between 97 and 101 there is no semiprimes,
a(31)=9042022037 because gap=9042022037-9042022097=60 and between 9042022037 and 9042022097 there is no semiprimes.
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Dec 24 2007
STATUS
approved