A076252 Integers k such that omega(k) = omega(k-1) + omega(k-2) + omega(k-3), where omega(n) is the number of distinct prime factors of n.

2310, 3990, 4290, 6090, 6270, 10010, 11550, 12810, 13650, 17094, 17940, 18270, 19380, 21930, 22110, 22770, 23100, 24990, 25410, 27300, 28644, 30090, 32214, 32604, 34034, 34314, 35340, 35880, 37310, 38190, 38570, 38640, 39270, 39780

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

omega(2310) = 5 = 1 + 2 + 2 = omega(2309) + omega(2308) + omega(2307), so 2310 belongs to the sequence.

Mathematica

omega[n_] := Length[FactorInteger[n]]; a = {}; Do[If[omega[n] == omega[n - 1] + omega[n - 2] + omega[n - 3], a = Append[a, n]], {n, 1, 10^5}]; a
Flatten[Position[Partition[PrimeNu[Range[40000]], 4, 1], _?(#[[4]] == Total[ Take[ #, 3]]&), {1}, Heads->False]]+3 (* Harvey P. Dale, Oct 31 2016 *)

Crossrefs

Cf. A001221, A006049, A076251, A076253.

Sequence in context: A136154 A376380 A258360 * A264718 A147572 A046303

Adjacent sequences: A076249 A076250 A076251 * A076253 A076254 A076255

Keyword

nonn

Author

Joseph L. Pe, Nov 04 2002

Status

approved