A076251 Numbers m such that omega(m) = omega(m-1) + omega(m-2), where omega(m) is the number of distinct prime factors of m.

3, 6, 10, 18, 30, 33, 42, 60, 66, 84, 90, 102, 105, 110, 114, 126, 129, 130, 138, 150, 165, 168, 174, 180, 195, 198, 210, 228, 234, 252, 264, 270, 273, 285, 290, 294, 315, 318, 330, 345, 348, 354, 360, 385, 399, 402, 420, 434, 450, 462, 465, 468, 480, 504

Offset

1,1

Links

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

Example

omega(18) = 2 = 1 + 1 = omega(17) + omega(16), so 18 belongs to the sequence.

Mathematica

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

Prog

(PARI) lista(kmax) = {my(o1 = omega(1), o2 = omega(2), o3); for(k = 3, kmax, o3 = omega(k); if(o3 == o1 + o2, print1(k, ", ")); o1 = o2; o2 = o3); } \\ Amiram Eldar, Sep 18 2024

Crossrefs

Cf. A001221, A076252, A076253.

Sequence in context: A182152 A170803 A182908 * A261631 A029864 A075111

Adjacent sequences: A076248 A076249 A076250 * A076252 A076253 A076254

Keyword

nonn

Author

Joseph L. Pe, Nov 04 2002

Status

approved