A101938 Numbers n with omega(n) < omega of 2 nearest larger and 2 nearest smaller neighbors.

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

Offset: 1

Author

Neil Fernandez, Dec 21 2004

Keywords

• easy
• nonn

Examples

			173 is in the sequence because it has one unique prime factor (itself), whereas
171, 172, 174 and 175 each have more.
		

Links

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

Crossrefs

Cf. A001221, A101934.

Programs

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 *)