OFFSET
1,1
COMMENTS
This sequence is based on a slightly weaker, but still unproved, version of Grimm's conjecture: If there is no prime in the interval [n+1, n+k], then the product (n+1)(n+2)...(n+k) has at least k distinct prime divisors. We have a(n) >= A059686(n), with the two sequences first differing at n=70. Computing a(n) is much faster than computing A059686.
It seems that Grimm's conjecture could have another (but not a weak) form: let p(1)...p(i) be a subset of prime numbers such that while n is integer, 0 < n < i, for any n, p(n) < p(n+1). Then there exists such sequence c(1)...c(i) where each term is a composite number, c(n+1) = c(n) + 1, and c(n) == 0 (mod p(n)). - Sergey Pavlov, Mar 21 2017
REFERENCES
See A059686
LINKS
T. D. Noe, Table of n, a(n) for n=1..1000
M. Waldschmidt, Open Diophantine problems, arXiv:math/0312440 [math.NT], 2003-2004, pages 6-7.
EXAMPLE
a(6) = 5 because 7*8*9*10*11 has 5 prime factors and 7*8*9*10*11*12 does not have 6 prime factors.
MATHEMATICA
Table[k=2; While[Length[FactorInteger[Times@@Range[n0+1, n0+k]]]>=k, k++ ]; k-1, {n0, 100}]
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
T. D. Noe, Nov 30 2004
STATUS
approved