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A076762 2-apexes of omega: n such that omega(n-2) < omega(n-1) < omega(n) > omega(n+1) > omega(n+2), where omega(m) = the number of distinct prime factors of m. 0
105, 165, 195, 315, 345, 399, 465, 1095, 1281, 1305, 1365, 1785, 1995, 2145, 2415, 2475, 2805, 3255, 3465, 3795, 3927, 4515, 4641, 4785, 4935, 5415, 5505, 5565, 5655, 5925, 5985, 6045, 6105, 6195, 6279, 6555, 6699, 6765, 6825, 7215, 7245, 7605, 7725 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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).

LINKS

Table of n, a(n) for n=1..43.

MATHEMATICA

omega[n_] := Length[FactorInteger[n]]; Select[Range[4, 10^4], omega[ # - 2] < omega[ # - 1] < omega[ # ] > omega[ # + 1] > omega[ # + 2] &]

CROSSREFS

Cf. A001222.

Sequence in context: A118678 A152940 A189936 * A036798 A119434 A091495

Adjacent sequences:  A076759 A076760 A076761 * A076763 A076764 A076765

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Nov 13 2002

STATUS

approved

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Last modified May 23 07:00 EDT 2019. Contains 323508 sequences. (Running on oeis4.)