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A076759 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 prime factors of m, counting multiplicity. 1
189, 315, 405, 675, 729, 891, 1029, 1053, 1269, 1376, 1395, 1485, 1683, 1701, 1755, 1845, 1863, 1875, 1917, 1995, 2025, 2205, 2349, 2457, 2475, 2691, 2709, 2805, 2835, 2925, 2997, 3003, 3075, 3125, 3267, 3315, 3375, 3465, 3525, 3576, 3591, 3675, 3861 (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.

EXAMPLE

Omega(187) = 2 < Omega(188) = 3 < Omega(189) = 4 > Omega(190)= 3 > Omega(191) = 1, so 189 is a 2-apex of Omega.

MATHEMATICA

Select[Range[4, 10^4], Omega[ # - 2] < Omega[ # - 1] < Omega[ # ] > Omega[ # + 1] > Omega[ # + 2] &]

CROSSREFS

Cf. A001222.

Sequence in context: A031901 A320709 A224674 * A178228 A211815 A292173

Adjacent sequences:  A076756 A076757 A076758 * A076760 A076761 A076762

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Nov 13 2002

STATUS

approved

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Last modified June 24 13:17 EDT 2019. Contains 324325 sequences. (Running on oeis4.)