%N Initial term of first run of exactly n consecutive numbers with 4 distinct prime factors.
%C The number of distinct prime factors is A001221.
%C a(23) = 585927201062; a(n) > 10^13 for n = 20, 21, 22, and n >= 24, if they exist.
%C Eggleton and MacDougall show that there are no more than 419 terms in this sequence.
%H Roger B. Eggleton and James A. MacDougall, <a href="http://www.jstor.org/stable/27643119">Consecutive integers with equally many principal divisors</a>, Math. Mag. 81 (2008), 235-248.
%H R. B. Eggleton, J. S. Kimberley, and J. A. MacDougall, <a href="http://hdl.handle.net/1959.13/35886">Principal divisor ranks of the first trillion positive integers</a>, NOVA: The University of Newcastle’s Digital Research Repository (2009).
%e a(6) > a(7) because the first run of 6 consecutive integers i with A001221(i)=4 is not maximal.
%Y Cf. A064709, A185032, and A087977.
%A R. B. Eggleton, _Jason Kimberley_, and J. A. MacDougall, Apr 12 2011