

A064708


Initial term of run of (at least) n consecutive numbers with just 2 distinct prime factors.


4




OFFSET

1,1


COMMENTS

It can be shown by an application of Mihailescu's theorem that a(12) does not exist, since then there would be two 3smooth numbers close together (it suffices to check up to 2*3^3).


REFERENCES

Roger B. Eggleton and James A. MacDougall, Consecutive integers with equally many principal divisors, Math. Mag 81 (2008), 235248. [From T. D. Noe, Oct 13 2008]


LINKS

Table of n, a(n) for n=1..8.


EXAMPLE

6 = 2*3; 14 = 2*7 and 15 = 3*5; 20 = 2^2*5, 21 = 3*7 and 22 = 2*11; 33 = 3*11, 34 = 2*17, 35 = 5*7 and 36 = (2*3)^2; etc.


CROSSREFS

Cf. A064709.
Sequence in context: A101567 A123267 A236928 * A064709 A118129 A046712
Adjacent sequences: A064705 A064706 A064707 * A064709 A064710 A064711


KEYWORD

nonn,fini


AUTHOR

Robert G. Wilson v, Oct 13 2001


EXTENSIONS

If a(9) exists, it is greater than 10^30.  Don Reble (djr(AT)nk.ca), Mar 02 2003
If a(9) exists, it is greater than 10^3000.  Charles R Greathouse IV, Apr 22 2009


STATUS

approved



