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%I #7 Feb 06 2020 07:14:17
%S 105,165,195,315,345,399,465,1095,1281,1305,1365,1785,1995,2145,2415,
%T 2475,2805,3255,3465,3795,3927,4515,4641,4785,4935,5415,5505,5565,
%U 5655,5925,5985,6045,6105,6195,6279,6555,6699,6765,6825,7215,7245,7605,7725
%N 2-apexes of omega: numbers k such that omega(k-2) < omega(k-1) < omega(k) > omega(k+1) > omega(k+2), where omega(m) = the number of distinct prime factors of m.
%C I call n a "k-apex" (or "apex of height k") of the arithmetical function f if n satisfies f(n-k) < ... < f(n-1) < f(n) > f(n+1) > .... > f(n+k).
%H Amiram Eldar, <a href="/A076762/b076762.txt">Table of n, a(n) for n = 1..10000</a>
%F 105 is a term since omega(105) = 3, omega(104) = omgea(106) = 2, and omega(103) = omega(107) = 1, so omega(103) < omega(104) < omega(105) > omega(106) > omega(107).
%t omega[n_] := Length[FactorInteger[n]]; Select[Range[4, 10^4], omega[ # - 2] < omega[ # - 1] < omega[ # ] > omega[ # + 1] > omega[ # + 2] &]
%Y Cf. A001222.
%K nonn
%O 1,1
%A _Joseph L. Pe_, Nov 13 2002
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