cp's OEIS Frontend

A380432 Numbers k such that bigomega(k) > omega(k) > 3.

%I A380432 #5 Jan 29 2025 12:22:40
%S A380432 420,630,660,780,840,924,990,1020,1050,1092,1140,1170,1260,1320,1380,
%T A380432 1386,1428,1470,1530,1540,1560,1596,1638,1650,1680,1710,1716,1740,
%U A380432 1820,1848,1860,1890,1932,1950,1980,2040,2070,2100,2142,2184,2220,2244,2280,2340,2380
%N A380432 Numbers k such that bigomega(k) > omega(k) > 3.
%C A380432 A200521 is a proper subset; a(144) = 4620 is not contained in A200521; A200521(144) = 4650.
%C A380432 Subset of A375055, which is in turn a subset of A126706.
%H A380432 Michael De Vlieger, <a href="/A380432/b380432.txt">Table of n, a(n) for n = 1..10000</a>
%e A380432 Table of select a(n) showing exponents listed in columns of primes written vertically in the heading. For p^0 we instead write "." for clarity:
%e A380432               Exponent of prime
%e A380432                      1 1 1 1
%e A380432    n   a(n)   2 3 5 7 1 3 7 9
%e A380432   -----------------------------
%e A380432     1    420   2 1 1 1
%e A380432     2    630   1 2 1 1
%e A380432     3    660   2 1 1 . 1
%e A380432     4    780   2 1 1 . . 1
%e A380432     5    840   3 1 1 1
%e A380432     6    924   2 1 . 1 1
%e A380432     7    990   1 2 1 . 1
%e A380432     8   1020   2 1 1 . . . 1
%e A380432     9   1050   1 1 2 1
%e A380432    10   1092   2 1 . 1 . 1
%e A380432    11   1140   2 1 1 . . . . 1
%e A380432    12   1170   1 2 1 . . 1
%e A380432   144   4620   2 1 1 1 1
%e A380432   190   5460   2 1 1 1 . 1
%e A380432   275   6930   1 2 1 1 1
%t A380432 Select[Range[2500], PrimeOmega[#] > PrimeNu[#] > 3 &]
%Y A380432 Cf. A001221, A001222, A126706, A200521, A375055.
%K A380432 nonn,easy
%O A380432 1,1
%A A380432 _Michael De Vlieger_, Jan 29 2025