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A076761 3-apexes of omega: n such that omega(n-3) < omega(n-2) < omega(n-1) < omega(n) > omega(n+1) > omega(n+2) > omega(n+3), where omega(m) = the number of distinct prime factors of m. 0
104006, 272986, 557480, 706706, 757316, 835016, 908600, 948310, 995554, 1093730, 1181410, 1198406, 1212694, 1252510, 1253330, 1283710, 1352560, 1370915, 1428686, 1440880, 1452836, 1513730, 1524446, 1627444, 1654730, 1662310 (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..26.

EXAMPLE

omega(104003), ..., omega(104006), ..., omega(104009) equal 1, 3, 4, 5, 3, 2, 1, respectively. Hence 104006 is a term of the sequence.

MATHEMATICA

omega[n_] := Length[FactorInteger[n]]; Select[Range[5, 10^6], omega[ # - 3] < omega[ # - 2] < omega[ # - 1] < omega[ # ] > omega[ # + 1] > omega[ # + 2] > omega[ # + 3] &]

okQ[{a_, b_, c_, d_, e_, f_, g_}]:=a<b<c<d>e>f>g; Flatten[ Position[ Partition[ PrimeNu[ Range[167*10^4]], 7, 1], _?(okQ[#]&)]]+3 (* Harvey P. Dale, Jul 27 2019 *)

CROSSREFS

Cf. A001222.

Sequence in context: A210180 A136312 A205260 * A236007 A129241 A290535

Adjacent sequences:  A076758 A076759 A076760 * A076762 A076763 A076764

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Nov 13 2002

EXTENSIONS

a(10)-a(26) from Donovan Johnson, Feb 07 2009

STATUS

approved

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Last modified January 19 00:40 EST 2020. Contains 331030 sequences. (Running on oeis4.)