A101294 Numbers n such that omega(n-2) = omega(n-1) = omega(n) = omega(n+1) = omega(n+2).

56, 93, 94, 117, 143, 144, 145, 146, 160, 207, 214, 215, 216, 217, 297, 303, 325, 326, 327, 393, 537, 687, 723, 801, 1137, 1347, 1467, 1537, 1713, 1943, 1983, 2103, 2217, 2304, 2305, 2306, 2427, 2643, 2666, 2716, 3867, 3914, 4413

Offset

1,1

Links

G. C. Greubel, Table of n, a(n) for n = 1..5000

Example

143 is in the sequence because it has two unique prime factors (11 and 13), the same number as its two nearest neighbors on both sides (141 has 3 and 47, 142 has 2 and 71, 144 has 2 and 3 and 145 has 5 and 29).

Mathematica

For[i=2, i<10000, 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[600000], PrimeNu[# - 2] == PrimeNu[# - 1] == PrimeNu[#] == PrimeNu[# + 1] == PrimeNu[# + 2] &] (* G. C. Greubel, May 15 2017 *)

Crossrefs

Cf. A001221, A101932.

Sequence in context: A104394 A353281 A101935 * A280932 A039534 A360332

Adjacent sequences: A101291 A101292 A101293 * A101295 A101296 A101297

Keyword

easy,nonn

Author

Neil Fernandez, Dec 21 2004

Extensions

Edited by N. J. A. Sloane, Mar 17 2007

Status

approved