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A101938 Numbers n with omega(n) < omega of 2 nearest larger and 2 nearest smaller neighbors. 2
37, 53, 64, 67, 89, 97, 113, 121, 131, 157, 163, 173, 211, 223, 233, 251, 263, 277, 289, 293, 307, 317, 331, 337, 343, 353, 367, 373, 379, 383, 389, 397, 401, 409, 439, 443, 449, 457, 467, 479, 487, 491, 499, 503, 509, 512, 529, 541, 547 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..10000

EXAMPLE

173 is in the sequence because it has one unique prime factor (itself), whereas

171, 172, 174 and 175 each have more.

MATHEMATICA

For[i=2, i<1000, If[And[Length[FactorInteger[i-2]]>Length[FactorInteger[i]], Length[FactorInteger[i-1]]>Length[FactorInteger[i]], Length[FactorInteger[i+1]]>Length[FactorInteger[i]], Length[FactorInteger[i+2]]>Length[FactorInteger[i]]], Print[i]]; i++ ]

Select[Range[6500], PrimeNu[#] < Min[PrimeNu[# - 1], PrimeNu[# - 2], PrimeNu[# + 1], PrimeNu[# + 2]] &] (* G. C. Greubel, May 15 2017 *)

CROSSREFS

Cf. A001221, A101934.

Sequence in context: A323476 A345169 A092105 * A060330 A302720 A304358

Adjacent sequences:  A101935 A101936 A101937 * A101939 A101940 A101941

KEYWORD

easy,nonn

AUTHOR

Neil Fernandez, Dec 21 2004

STATUS

approved

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Last modified December 8 20:37 EST 2021. Contains 349596 sequences. (Running on oeis4.)