This site is supported by donations to The OEIS Foundation.



Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A117969 Start of least run of maximal length of consecutive n-almost primes. 0
2, 33, 211673, 97524222465 (list; graph; refs; listen; history; text; internal format)



For n>=2 there cannot be more than 2^n - 1 consecutive n-almost primes. Is it known whether there always exists such a run of length 2^n - 1? If not, I conjecture so. This is confirmed to be true for terms through a(4). Terms here equal the last terms of corresponding finite sequences: a(3) = A067813(6). a(4) was computed by Don Reble as A067814(14). a(5) >= A067820(12).

a(4) is smaller than the number 488995430567765317569 found by Forbes. [From T. D. Noe, Oct 29 2008]


Table of n, a(n) for n=1..4.

Tony Forbes, Fifteen consecutive integers with exactly four prime factors, Math. Comp. 71 (2002), 449-452. [From T. D. Noe, Oct 29 2008]


a(2) = 33 because 33, 34, 35 is the least run of three consecutive 2-almost primes (semiprimes).


Cf. A067813, A067814, A067820, A067821, A067822.

Sequence in context: A083459 A034173 A132519 * A003820 A112980 A109336

Adjacent sequences:  A117966 A117967 A117968 * A117970 A117971 A117972




Rick L. Shepherd, Apr 05 2006



Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 18 16:40 EST 2019. Contains 319271 sequences. (Running on oeis4.)