login
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.
8
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
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.
Sequence in context: A182152 A170803 A182908 * A261631 A029864 A075111
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Nov 04 2002
STATUS
approved